Systematic Review of Healthy Eating Interventions and Diabetes 1
Diabetes and Healthy Eating: A Systematic Review of Dietary Interventions
Rachel Clare Povey, B.Sc., Ph.D. &
David Clark-Carter, B.Sc., M.Ed., Ph.D.
Centre for Health Psychology, Staffordshire University, Stoke-on-Trent, U.K.
Running head: Systematic review of healthy eating and diabetes
Address of corresponding author:
Dr Rachel Povey
Centre for Health Psychology
Faculty of Sciences
Staffordshire University
Stoke-on-Trent
ST4 2DE
United Kingdom
Tel: +44 (0)1782-294570 e-mail: [email protected] Systematic Review of Healthy Eating Interventions and Diabetes 2
Abstract
Objective
The objective was to review the literature on healthy eating interventions within diabetes care as the state of evidence exists.
Data Sources
The databases PubMed, Cumulative Index to Nursing and Allied Health Literature, and
PsycINFO were searched for the terms “(“healthy eating” or “dietary”) and intervention and diabetes” in the abstracts. In addition, electronic searches of the contents of the specific journals Diabetes, Clinical Diabetes, Diabetes Care, Diabetes Spectrum and
Diabetic Medicine were conducted.
Study Selection
Papers were included in the review if the participants were diagnosed with type 1 or type 2 diabetes; results from an intervention to promote dietary change were reported; measurements were taken from two time points: pre- and post-intervention; at least one outcome measured eating behavior; and the articles had been published between 1990 and the present date. Articles were excluded if: they had not been peer reviewed; they were cross-sectional studies; they were descriptive articles such as reviews, advice, lectures or conference proceedings; they were not written in English; they did not use human participants; and the intervention was targeted towards a group which was so specific that the extent to which it could be applied to a general population with diabetes Systematic Review of Healthy Eating Interventions and Diabetes 3 was reduced. Finally samples were not restricted to the United States only, or to any specific age group. After retrieval, one further criterion was added, which stated that any study which did not “include some type of individualized assessment, development of a plan, and periodic reassessment between instructor(s) and participant when directing the selection of appropriate education materials and intervention” was excluded.
Data Extraction
Data were extracted from eligible studies. Each paper included in the review was scrutinized thoroughly and methodically by two independent reviewers, and the relevant data extracted. During this process, two articles were removed, as under closer scrutiny it was found that they did not meet all the inclusion criteria. The total number of articles which were reviewed was 23.
Data Synthesis
Studies included a wide range of outcome measures, making direct comparison between studies difficult. To complicate the issue further, studies varied in how the outcome was assessed or reported. However, results from studies were compared by examining the characteristics of those studies which produced a statistically significant result, with those which did not for the different outcome measures. To make the task more manageable this process was limited to those outcomes which had been measured by at least six studies. Studies were compared in terms of sample types and sizes, duration, and type and content of intervention. Systematic Review of Healthy Eating Interventions and Diabetes 4
Conclusions
Comparisons between significant and non-significant studies revealed some interesting differences between them, although there did not appear to be any clear patterns across the different outcomes, making it difficult to identify any clear distinctions.
However, for studies measuring the outcomes of weight, fat intake saturated fat intake, and carbohydrates, there was a tendency for successful interventions to include an exercise dimension, and group work. There was no clear pattern for sample size or duration of studies. However, it is interesting that some outcomes were more likely to show significant changes in studies of longer duration (e.g. serum cholesterol); whereas others were more likely to show significant changes in studies of shorter duration (e.g. weight, fiber), suggesting that certain behavioral outcomes may be more difficult to maintain. Future research would benefit by ensuring sample sizes are adequate to give sufficient power, and also by including outcomes in the four different areas of learning, behavior, clinical improvement and health status. In addition, interventions should be designed which focus on the maintenance, in addition to the initiation of eating behavior change. Systematic Review of Healthy Eating Interventions and Diabetes 5
Introduction
There is now good evidence to show the benefits of healthy eating for those with diabetes, including improvement in blood glucose control, improvement of lipid profiles, maintenance of blood pressure in the normal range, and weight loss or maintenance1.
Such evidence has led the American Diabetes Association to describe medical nutrition therapy as an “integral component of diabetes self-management education (or training)”
1, the goal of which has been described as aiming to “assist and facilitate individual lifestyle and eating behavior changes”, leading to “improved metabolic control, a reduced risk in complications and improved health” 2. In addition, the adoption and maintenance of healthy eating has been identified as a key topic that should be given high priority in future research3, with particular research attention paid to issues concerning how to develop healthy eating habits as well as strategies for modifying unhealthy behaviors4.
There currently exist a large number of studies which have delivered healthy eating and dietary change interventions in a range of settings. These utilise many different mechanisms to promote dietary change, ranging from those which take a prescriptive approach, to those which have taken more of a patient-centered empowerment approach5. Additionally, such studies have used a range of outcome measures to examine the effectiveness of interventions, varying from behavioral outcomes such as changes in nutrients (e.g., fat and fiber intake), to clinical outcomes such as hemoglobin
A1c (HbA1c), and weight. However, until this literature is reviewed systematically, and the effectiveness of such interventions documented6, it is impossible to derive any Systematic Review of Healthy Eating Interventions and Diabetes 6 specific conclusions regarding the relative effectiveness of the mechanisms of such interventions, and this is what this paper seeks to do.
The central objective of this paper is to review systematically published reports of healthy eating interventions in diabetes care since 1990. The ultimate aims are to evaluate the effectiveness of the mechanisms of different healthy eating interventions for people with diabetes, and where possible to provide guidance to diabetes educators intending to promote healthy eating, and to identify new directions for the development of future research.
Methods
Searching
The following databases were searched for the terms “(“healthy eating” or “dietary”) and intervention and diabetes” in the abstracts: PubMed (03/13/06), Cumulative Index to
Nursing and Allied Health Literature (Cinahl; 03/13/06), and PsycINFO (02/15/06).
Further limits were imposed where possible, to English Language only (Cinahl;
PubMed), peer reviewed (Cinahl), and humans only (Pubmed). Finally searches using the same terms were carried out electronically for the specific journals Diabetes,
Clinical Diabetes, Diabetes Care, Diabetes Spectrum and Diabetic Medicine as these were considered to be journals highly relevant to the subject area.
Selection
Abstracts were included in the review if: they were original articles; the participants were Systematic Review of Healthy Eating Interventions and Diabetes 7 diagnosed with type 1 or type 2 diabetes; results from an intervention to promote dietary change were reported; measurements were taken from two time points: pre- and post- intervention6; at least one outcome measured dietary behavior; and the articles had been published between 1990 and the present date. Articles were excluded if: they had not been peer reviewed; they were descriptive articles such as reviews, advice, lectures or conference proceedings; they were not written in English; they did not use human participants; and the intervention was targeted towards a group which was so specific that the extent to which it could be applied to a general population with diabetes was reduced. Articles were also excluded if they reported cross-sectional studies, as this type of study design did not make it possible to examine the impact of an intervention on outcomes over a period of time. Finally, samples were not restricted to the United
States only, or to any specific age group.
In the first instance, two independent reviewers (the authors) read all the abstracts resulting from the database searches and agreed on whether or not they would be selected for the review. Full text copies of the articles were retrieved, unless they were rejected during this initial screening process. They were rejected if there was enough information in the abstract to demonstrate that they did not meet the inclusion criteria, or that they fulfilled one or more of the exclusion criteria. Once retrieved, each of the articles was scrutinized separately by the two reviewers to check whether it met the inclusion and exclusion criteria. At this stage, one further exclusion criterion was included, to meet the nutrition principles and recommendations of the American
Diabetes Association7 and also to meet Standard 8 of the National Standards for Systematic Review of Healthy Eating Interventions and Diabetes 8
Diabetes Self-Management Education8. This criterion therefore stated that any study which did not “include some type of individualized assessment, development of a plan, and periodic reassessment between instructor(s) and participant when directing the selection of appropriate education materials and intervention” was excluded. This also served to remove all those studies which compared prescribed diets. This therefore enabled us to focus our review on the differences in effectiveness of the mechanisms of the different types of interventions used to promote healthy eating and dietary change, rather than on the differences in the effectiveness of different prescribed diets. Any articles that did not meet all the criteria were excluded from the final review.
Validity Assessment
Quality assessment of evidence for each eligible article was determined using the
American Diabetes Association evidence grading system9. Evidence was divided into three levels: A, B, or C. Articles which were graded “A” were based on large well- conducted, generalizable, randomized controlled trials that were adequately powered; articles which were graded “B” provided supportive evidence from well-conducted cohort studies, or well-conducted case-control studies; and articles which were graded
“C” provided supportive evidence from poorly controlled or uncontrolled studies. All articles were assessed for quality by the two independent reviewers, and any disagreements in categorization discussed.
Data Abstraction
Data were extracted from the eligible studies. Each paper included in the review was Systematic Review of Healthy Eating Interventions and Diabetes 9 scrutinized thoroughly and methodically by the two independent reviewers, and the relevant data extracted. During this process, two extra articles were removed, as under closer scrutiny it was found that they did not meet all the inclusion criteria10, 11.
Study Characteristics
Data extracted from the final eligible studies included descriptive information (i.e. diagnosis, age (mean and standard deviation/range where available), gender, setting, description of sample); information about the methodology (i.e. description of intervention and control conditions, recruitment methods, study design, method of allocation to study conditions); and finally details of the relevant outcome measures.
Outcomes were defined in terms of learning (e.g. change in knowledge or skills); behavior changes (e.g. change in fat intake or fruit and vegetable intake); clinical improvement (e.g. change in glycemic control or weight); or improved health status (e.g. quality of life, or well-being) in line with the standards proposed by the American
Association of Diabetes Educators2, 6. Notes were also taken regarding possible confounding effects and limitations of the different studies.
Data Synthesis
Results from studies were compared by examining the characteristics of those studies which produced a statistically significant result (“successful” studies), with those which did not (“unsuccessful” studies) for the different outcome measures. To make the task more manageable this process was limited to those outcomes which had been measured by at least six studies. Studies were compared in terms of sample types and Systematic Review of Healthy Eating Interventions and Diabetes 10 sizes, duration, and type and content of intervention.
Results
Trial Flow
The total number of potentially relevant articles identified from all databases and abstracts screened for retrieval was 497 abstracts (totals: PubMed 357 abstracts,
Cinahl 76 abstracts, PsycINFO 17 abstracts, specific diabetes journals 47 abstracts).
From these 497 abstracts, 86 articles were retrieved for more detailed evaluation (33 were cited by more than one database). After retrieval, a further 61 were excluded from the systematic review (for not fulfilling the inclusion/exclusion criteria), resulting in a total number of 25 where data were to be extracted. During the data extraction process, two additional articles were removed, as under closer scrutiny it was found that they did not meet all the inclusion criteria10, 11. Finally, a further three studies were found to be reporting results from the same sample as other papers which were already included 12,
13, 14, these were therefore removed for the purpose of analysis. For full list of 86 articles, and details of reasons why specific papers were excluded, please see Appendix. A profile summarizing trial flow can be seen in Figure 1.
Figure 1 about here
Study Characteristics
Outcome measures were classified into variables measuring learning, behavior change, clinical improvement and improved health status in line with the standards proposed by Systematic Review of Healthy Eating Interventions and Diabetes 11 the American Association of Diabetes Educators2, 6. However, there was a wide range of outcome measures (65 in total), making direct comparison between studies difficult.
Outcomes within each of the four categories were extremely varied. For example, outcomes measuring learning included measures of nutritional15 or diabetes knowledge16 or knowledge of self-care17; those measuring behavior change included measures of dietary fat, cholesterol, carbohydrate and energy intake (kilocalories)18; those measuring clinical improvement included measures of weight, blood pressure and
HbA1c19; and finally those measuring improved health status included measures of psychological well-being and depression20. To complicate the issue further, studies varied in how the outcome was assessed or reported. For example, those reporting intake of fat varied from measuring percentage of kilocalories eaten in the form of fat, to proportion of fat-related items from a food questionnaire.
Table 1 summarises the different outcome measures taken, the number of studies which used each measure, and the number which found a statistical difference.
Table 1 about here.
In addition to there being a variety of outcomes measured, the interventions differed in a number of other aspects. These included: whether they were part of a more general intervention into lifestyle (including looking at exercise), or whether they targeted specific aspects such as weight or risks for coronary heart disease, or specific groups based on ethnicity or a medical condition; whether they dealt with aspects of psychology Systematic Review of Healthy Eating Interventions and Diabetes 12 such as self-efficacy, looking at healthy eating barriers, problem solving, or stages of change; whether they employed a particular approach to learning such as only tackling a limited number of concepts at a time, concentrating on skills, providing feedback about laboratory results or using behavior modification. Also, the interventions differed in terms of how they were delivered: whether computers were used to communicate with participants or to deliver the intervention; whether participants could communicate with those running the program by telephone; whether discussion groups or videos were employed; whether peer counsellors were involved; whether a dietitian or nutritionist delivered the intervention; and whether specific recipes were provided (and if so, whether they came from the participants or those running the study). Finally, the nature of the samples differed in terms of age, gender, ethnicity, and type of diabetes.
Although type 1 and type 2 diabetes are metabolically different with different eating priorities, only two studies27, 32 specifically examined people with type 1 diabetes alone.
As it would be inappropriate to carry out between group comparisons on such small numbers, it was decided to combine the studies for the purpose of this review. See
Table 2 below for descriptions of the specific studies included in the final review.
Table 2 about here
Data Synthesis
There was 91.9% agreement between the reviewers for the 86 articles reviewed, with consensus reached for the remaining seven articles through discussion. Agreement on quality criteria on the final 23 articles was moderate, with 75% agreement between the Systematic Review of Healthy Eating Interventions and Diabetes 13 two reviewers. Disagreement over the remaining articles was due to the fact that they did not fit neatly into any of the three possible categories, but again, consensus was reached by discussion.
Given the heterogeneity of studies, in an attempt to distinguish studies which did produce a statistically significant result from those which did not, characteristics of each type of study were explored. However, the multi-dimensional nature of healthy eating behavior resulted in a total of 65 dietary outcomes measured for the different studies
(with 16 different measures of nutrient intake; see Table 1). In order to make the comparison between studies more manageable, results are therefore reported only for those outcomes which have been measured by at least six studies.
Weight
There were three significant12, 19, 22 and nine non-significant studies16, 18, 23-28, 31. Two of the three significant studies involved an exercise element12, 22, while only four out of the nine non-significant studies involved exercise16, 23, 27, 28. One additional study21, which involved drugs and exercise, found a statistically significant increase in weight with intensive therapy, despite significant reductions in total energy in both groups. It was argued that a possible reason for this discrepancy may be under-reporting of food intake within the sample. The sample size was slightly smaller for the significant studies
(mean = 118.3, SD = 141.5 versus mean =125.7, SD = 146.5) and the duration was shorter (mean = 0.55 years, SD = 0.42 versus mean = 0.69 years, SD = 0.46). The focus of the significant studies was very different, varying from a Mediterranean Systematic Review of Healthy Eating Interventions and Diabetes 14
Lifestyle Program12, where participants attended weekly meetings for 6 months, consisting of a combination of physical activity, stress management, tips for adhering to a Mediterranean diet and support groups; to an intervention where participants received intensive, personalized nutrition counseling in order to follow either high protein or high carbohydrate diets19; to an intervention specifically designed for overweight African-
Americans22, where each participant received an individualized weight reduction diet, and attended 12 weekly group sessions, one individual diet counseling session, and six bi-weekly group sessions. Whereas none of the significant studies included anyone with type 1 diabetes, two of the non-significant studies did24, 27. Two12, 22 of the three significant studies involved some form of group work, while only two of the nine non- significant studies involved an element of group work16, 23. The study which showed a significant weight gain21 included group work which involved spouses and lasted four years.
HbA1c
There is no obvious pattern to distinguish the significant and non-significant studies.
Two21, 22 out of the seven significant studies17, 19, 21-24, 26 involved an exercise component, one consisting of advice about exercise activities, positive feedback and educational exercises21 (this study also involved drugs (“polypharmacological therapy”)), and the other consisting of 20 minutes of low impact aerobic activity22. Two16, 33 of the nine non- significant studies16, 18, 20, 25, 29-33 also involved exercise. An additional study, which also included exercise27, showed inconsistent results in that one group showed no significant change over the intervention, whereas a crossover group subsequently given the same Systematic Review of Healthy Eating Interventions and Diabetes 15 intervention did show a significant improvement. In this group, there was little change in
HbA1c levels in the first 6 months when they were receiving standard care, but the levels decreased significantly (p=0.002) over the following 6 months, when the group received intensive dietary advice. Sample size could not be seen as an explanation for the difference (significant studies: mean sample size = 139.85, SD = 165.99; non- significant studies: mean = 118.33, SD = 79.84; the smallest sample among the significant studies19 was 12, whereas for the non-significant studies the smallest sample32 was 32). Although the mean duration of treatment was longer for the significant studies this was due to one significant study21 lasting four years and so duration could not be seen as an explanation, where this could be ascertained (one significant study failed to give details of duration17 and two non-significant studies provided imprecise information about it29, 32; significant studies: mean duration = 1.04 years, SD = 1.48; non-significant studies: mean = 0.79 year, SD = 0.42). Two of the significant studies only lasted eight weeks. Finally, four of the significant studies 17, 21, 22,
23 and four of the non-significant studies, involved groups16, 20, 29, 32.
Fasting blood glucose
For this measure it is also difficult to draw any conclusions about factors which might make a study successful or unsuccessful as there were only two non-significant studies17, 28 and one failed to give the exact duration17. One of these studies17 compared
183 participants who took part in an educational program consisting of a mixture of individual and group sessions, with 95 participants from a control group. Although the intervention group showed no significant reduction in fasting blood sugar levels, it is Systematic Review of Healthy Eating Interventions and Diabetes 16 interesting that it did, however, demonstrate a significant reduction in HbA1c levels.
The five significant studies18, 19, 23, 26, 32 had a mean sample size of 31.80 (SD = 30.20) and mean duration of 0.43 years (SD = 0.40); one study gave insufficient detail about duration32. The non-significant studies had sample sizes of 278 and 8. One of the non- significant studies involved exercise28, whereas none of the significant studies did. One of the significant studies had used a selection criterion that the participants should be newly diagnosed with blood glucose levels of 6.7mmol/L or greater in repeated measurements18. Two of the significant studies23, 32, and one of the non-significant studies17 involved groups.
Triglycerides
Three of the eight studies produced significant results18, 21, 25. Results showed serum triglycerides to decrease significantly within an intensified dietary education intervention18, and a multifactorial intervention consisting of behavior modification and polypharmacological therapy21. In the third study25, triglycerides were found to decrease significantly in a weight management group from recruitment to month 18, but no significant differences were found for participants allocated to modified lipid, or high carbohydrate diets. Triglyceride levels were also found to be significantly lower in the weight management group than in the high carbohydrate group throughout the study.
What seems to characterize the significant studies is a longer duration combined with a larger sample size (mean duration = 2.17 years, SD = 1.61 years; mean sample size =
99.00, SD = 44.44). In contrast, the non-significant studies19, 22, 23, 26, 27 had a mean sample size of 33.60 (SD = 26.44) and mean duration of 0.34 years (SD = .18). Even Systematic Review of Healthy Eating Interventions and Diabetes 17 though the mean duration for the significant studies was inflated by one lasting four years21, the shortest duration of any of them was one year18 whereas the longest duration of the non-significant studies was six months22, 27. One21 of the significant studies involved advice about exercise activities, where participants were urged to start or continue exercise by positive feedback and educational exercises, and polypharmacological therapy. Two of the non-significant studies also involved exercise22, 27 and none involved drugs. Only one significant study21 involved some group work, while two of the non-significant studies did22, 23
Serum Cholesterol
The three significant studies21, 30, 31 had good sized samples (mean = 205.33, SD =
59.18) and durations (mean = 1.75 years, SD = 1.95), and only one included exercise 21
(this study also included polypharmacological therapy). Two16, 22 of the nine non- significant studies included exercise interventions. The mean sample size for the non- significant studies16, 18, 19, 20, 22, 23, 25, 26, 29 was 69.33 (SD = 54.50) and the mean duration was 0.62 years (SD = 0.44). One of the significant studies21 and five of the non- significant studies involved some group work16, 20, 22, 23, 29. This group work varied from an educational approach based on the needs of participants and their spouses in the significant study21, to community-based group sessions16, a peer-directed discussion forum20, sessions focusing on nutrition education and exercise22, and peer-professional discussion groups23, 29 in the non-significant studies. An additional study, which included exercise27, showed inconsistent results in that one group showed no significant change over the intervention, whereas a crossover group subsequently given the same Systematic Review of Healthy Eating Interventions and Diabetes 18 intervention did show a significant improvement.
High Density Lipoproteins (HDL)
One27 of the four significant studies18, 19, 25, 27 included an element of exercise by providing participants with intensive lifestyle education for six months consisting of individualized dietary and exercise programs. Participants went to monthly meetings with the research team consisting of reinforcement of advice, feedback on laboratory results and the use of behavior modification techniques to improve metabolic control.
Three16, 21, 22 of the five non-significant studies16, 21-23, 26 also involved exercise interventions (one of which also included a drug intervention21). There was no advantage in terms of sample size or duration for the significant studies (mean sample size = 55.25, SD = 30.59, mean duration 0.79 years, SD = 0.59) over the non-significant studies (mean sample size = 83.00, SD = 73.44; mean duration = 1.21 years, SD =
1.59). The higher mean duration in the non-significant studies is inflated by one study which lasted four years21. None of the significant studies involved groups, while four of the non-significant studies did16, 21-23.
Low Density Lipoproteins (LDL)
Two of the six studies19, 22, 23, 25-27 which measured LDL cholesterol were statistically signficant19, 27. One of these studies19 compared participants on high protein (40% carbohydrate, 30% protein, 30% fat) and high carbohydrate (55% carbohydrate, 15% protein, 30% fat) diets, and found a significant decrease in level of LDL cholesterol only in the high protein group. The other study27 examined an intensive lifestyle education Systematic Review of Healthy Eating Interventions and Diabetes 19 intervention and showed inconsistent results in that one group showed no significant change over the intervention, whereas a crossover group subsequently given the same intervention initially showed a significant increase in LDL cholesterol whilst receiving standard care, and later showed a significant decrease in LDL cholesterol. There was wide overlap between the sample sizes of the significant (mean = 36.50, SD = 34.65) and non-significant studies (mean = 39.75, SD = 28.00) and between their durations
(significant studies mean = 0.32 years, SD = 0.24; non-significant studies mean = 0.64 years, SD = 0.59). One of the significant studies27 and one of the non-significant studies22 involved exercise. Neither of the significant studies involved group work, whereas two of the non-significant studies did22, 23.
Kilocalories
There were four significant17, 27, 30, 35 and six non-significant16, 18, 19, 21, 25, 26 studies which measured kilocalories as an outcome, with an additional study22 which found an initially significant result after half the intervention had been completed, but a non-significant result after the full duration of the intervention. Interventions which found a significant improvement included displays of suitable food and general advice on meal planning 17, specific targets for dietary goals, information on nutrition, timing of meals, eating out, reading of food labels, adapting recipes and use of artificial sweeteners plus feedback from laboratory results27, touchscreen computer-assisted assessment of likely barriers to healthier eating and targets for a specific aspect of diet , e.g. fat intake30 and a focus on skills to promote change, with specific targets for dietary fat, saturated fat, cholesterol and fiber and demonstrations of food preparation and identification of Systematic Review of Healthy Eating Interventions and Diabetes 20 potential problems, help with label reading and analysis of low-fat meals 35. Among the studies which did not find a significant improvement in kilocalories was one which specifically concentrated on improving intake of fat, saturated fat and carbohydrates 16; one which had goals and targets for weight, normoglycemia, correction of dyslipidemia, blood pressure, and intake of fats, cholesterol, carbohydrates, fiber and sucrose18; one which placed participants in high protein or high carbohydrate conditions and gave calorie restricted alternatives for meals and advice on serving sizes 19; one which targeted intake of carbohydrates and fats, gave advice on portion size and introduced new foods21; one which targeted BMI with specific groups either concentrating on weight management, lipids, or carbohydrates and fiber where all were shown food displays and given advice on adapting favorite recipes25; and one which concentrated on weight maintenance but had targets for balance of carbohydrates, protein, fat and amount of fiber26. There was no strong pattern apart from difference in sample size to distinguish them. There was a big difference in mean sample size, with the mean sample size for the significant studies being 144.25 (SD = 114.33), with durations of 6, 9 and at least 7 months (one was not given17). For non-significant studies, on the other hand, the mean sample size was almost half: 82.50 (SD = 66.52) with a mean duration of 1.30 years
(SD = 1.42). Only one of the four significant studies included exercise 27, and two of the non-significant studies included an exercise intervention16, 21, with one of these also including a drug intervention21. Two of the significant studies17, 35 and three of the non- significant studies16, 21, 22 involved groups. One of these significant studies17 encouraged family members to attend the sessions and found, in the intervention group post- intervention, a significantly higher proportion reduced their total calorie intake when they Systematic Review of Healthy Eating Interventions and Diabetes 21 detected that they were overweight compared with prior to the intervention; there was not a significant reduction in the control group. The other significant study 35 analyzed kilocalorie intake and, adjusting for baseline intake, found that after three months the intervention group had a significantly lower intake of kilocalories than the control group.
Fat
There were ten significant17, 21, 22, 24, 26, 27, 30, 31, 34, 35 and four non-significant18-20, 25 studies measuring fat intake. Among the significant studies, one17 used booklets on meal planning and general health care and presented food displays of meals suitable for people with diabetes. In the intervention group only, they found that a significantly higher proportion of the participants post-intervention reported cutting down on oily/fatty food compared with pre-intervention. Another study21 was specifically aimed at fat and carbohydrate intake, giving advice on portion size, new foods and menus. It found that both intensive and control (standard treatment) groups had significantly reduced total fat
(as a percentage of energy intake) but that the intervention group had significantly lower intake than the control group. A further study22 also included targets for fat and carbohydrate intake. Advice was based on the culture of the participants and on recipes provided by participants. This included advice on meal planning, food shopping, label reading and food selection at restaurants. It found a significant difference between the usual care and intervention groups in change scores between baseline and three months but the difference was not significant at six months. Another study 26 had specific targets for the proportions of carbohydrate, protein and fat in the diet. It found a significant reduction in the amount of fat intake. However, there was no control group to Systematic Review of Healthy Eating Interventions and Diabetes 22 compare this result with. A further study27 gave out booklets which contained information on nutrition, the timing of meals, eating out, reading food labels and adapting recipes. There were specific targets for intake of carbohydrates, fat and fiber, feedback from laboratory results was given and behavior modification techniques were used. It used a crossover design whereby one group received an intervention for six months followed by six months of usual care while the other received usual care for six months followed by an intervention for six months. Both groups had reduced fat intake significantly after six months, with the intervention group having a significantly lower intake than the other group. At twelve months, intake was compared with the six month levels. The group which had been given the intervention followed by usual care showed a further significant reduction in intake, whereas the other group which was now in the intervention phase did not show a significant improvement. The next study 30 used a touch screen to identify dietary barriers and gave feedback on potential problem areas for diet. This was followed by individual sessions which set goals and gave advice on problem solving. Participants were split into two groups depending on their self-efficacy scores and the groups were shown a video which was adapted for their group. Both videos looked at strategies for dealing with barriers to healthy eating, with those with lower self-efficacy having their video presented in an interactive format. The data for the two self-efficacy groups were combined and post-intervention consumption rates were adjusted to allow for baseline rates. The intervention groups had significantly better intake than the usual care group. Another study31 had four conditions, each of which received a touch screen assessment and tailored feedback at the start of the program and after three months. One group received no more than this, one group Systematic Review of Healthy Eating Interventions and Diabetes 23 received telephone follow-up, one group received community support, including details of community resources and four newsletters, and one group had a combination of telephone follow up and community resources. The researchers report a significant improvement in fat intake in the telephone follow-up conditions. The next study 34 was looking specifically at reducing coronary heart disease risks and recommending a
Mediterranean diet (alpha-linolenic acid rich). According to a fat and fiber questionnaire, the intake of the intervention group, adjusted for baseline level, was significantly better than for the usual care condition. The final significant study 35 focused on skills to promote dietary change using Bandura’s social learning theory. It had specific targets for intake of various aspects of diet, including fat and involved demonstrations of food preparation, shopping and eating practices. Adjusting for baseline kilocalorie intake, the intervention group had significantly lower fat intake than the control group. There does not appear to be any pattern of differences between studies here, apart from sample size. The mean sample size for significant studies was
179.60 (SD = 138.87), with a mean duration of 1.05 years (SD = 1.23; for 8 studies: one not given17, another “at least 7 months”35). The mean sample for non-significant studies, on the other hand was 73.25 (SD= 50.08), with a mean duration of 0.73 years (SD =
0.64). Significant studies were therefore more likely to have bigger samples, and the interventions were more likely to last for longer. However, there is large overlap in the range of durations between the significant and non-significant studies. Four of the interventions in the significant studies also included an exercise component21, 22, 27, 34
(one of which also included drugs21), whereas none of the non-significant interventions included exercise. Five of the significant studies involved groups 17, 21, 22, 34, 35, while only Systematic Review of Healthy Eating Interventions and Diabetes 24 one of the non-significant studies involved some group work20.
Saturated Fat
There were seven significant18, 21, 22, 27, 30, 34, 35 and three non-significant16, 19, 25 studies which measured saturated fat intake. All the significant studies were also significant for fat intake, apart from one18 which had goals and targets for weight, normoglycemia, correction of dyslipidemia, blood pressure, and intake of fats, cholesterol, carbohydrates, fiber and sucrose. As well as information on the principles of diets for people with diabetes, it involved attempts to modify behavior via improving motivation and recognizing difficult situations such as parties and travelling. The intervention group was found to have significantly lowered saturated fat intake, while the conventional treatment group did not show a significant improvement. In addition, although the means and standard deviations are not reported in the article to any decimal places, a t-test based on the figures reported shows that the intervention group had a significantly lower fat intake than the conventional treatment group (t (82) = 2.04, p
= .04, d = 0.45). There were large amounts of overlap between the significant and non-significant groups, for both sample size and duration with differences between the means being accentuated by one significant study having a particularly long duration 21
(4 years) and one non-significant study having a particularly short duration (8 weeks) and small sample (12)19. For significant interventions, mean sample size was 125.00
(SD = 81.93); whereas for non-significant interventions, mean sample size was 82.33
(SD = 81.07). The duration for significant interventions varied between 6 months 27 and
4 years21 (mean = 1.29 years for 6 studies; SD = 1.35: the other was at least 7 Systematic Review of Healthy Eating Interventions and Diabetes 25 months35) whereas for non-significant studies, the duration varied between 8 weeks 19 and 18 months25 (mean = 0.88 years; SD = 0.68). Finally, four of the significant interventions also included an exercise component: One21 (which also included drugs) encouraged participants by ‘positive feedback and by educational exercise’, giving the example of demonstrations of the immediate lowering effect on blood glucose of moderate physical activity. Another22 had participants take 30 minutes of exercise during the sessions with the researchers and encouraged them to exercise for two additional days per week. Another study27 individualized the activity and duration of exercise depending on the participant’s level of fitness and goals. Finally, one study34 started with the goal of 30 minutes of moderate exercise on ‘most days of the week’ but once this had been achieved the goal was extended to one hour’s moderate aerobic activity per day. Only one of the non-significant interventions included exercise16. Four of the significant studies involved group work21, 22, 34, 35, while only one of the non- significant studies involved groups16.
Carbohydrates
Four significant studies19, 21, 27, 35 and three non-significant studies18, 25, 26 measured carbohydrate intake. An additional study22 showed significance after half the duration of the intervention but this became non-significant after the full duration of the study.
There was little difference between them in mean sample size, for significant interventions, the mean sample size was 65.00 (SD = 59.47), whereas for non- significant interventions, the mean sample size was 54.33 (SD = 35.50). The mean duration for significant interventions, however, was almost twice that of non-significant Systematic Review of Healthy Eating Interventions and Diabetes 26 interventions (mean duration for significant interventions = 1.55 yrs; SD = 2.13, with one study which lasted “at least 7 months duration”35; mean duration for non-significant interventions = 0.88 yrs; SD = 0.68). However, it should be noted that one of the significant interventions lasted for 4 years21, therefore inflating the mean. Three of the significant studies included an exercise component21, 22, 27, whereas none of the non- significant studies did. Three of the significant studies involved groups 21, 22, 35, with one including spouses21, while none of the non-significant studies involved any group work.
Fiber
Three significant studies17, 19, 26 and five non-significant studies18, 22, 25, 27, 35 measured fiber intake. Among the significant studies, one17, which took place in Singapore, asked specifically about intake of unpolished rice as well as other high fiber foods and found that there was a significant increase in the percentage in the intervention group but not in the control group. One study19 compared participants on high protein (40% carbohydrate, 30% protein, 30% fat) and high carbohydrate (55% carbohydrate, 15% protein, 30% fat) diets, and found that the high carbohydrate group had significantly lower intake of fiber (mean = 15 grams/day standard error = 1) than the high protein group (mean = 18 grams/day, standard error = 1). The other significant study26 had a recommended target of 35 grams of fiber in the diet. After the intervention, participants had significantly increased fiber intake to a mean of 32.7 grams (standard error = 1.1)
(as ascertained by 24-hour ‘dietary recall’ to evaluate pre-intervention intake and three- day dietary record for post intervention intake). There was no control condition for comparison. There was little difference in sample size (significant studies: mean = Systematic Review of Healthy Eating Interventions and Diabetes 27
101.67; SD = 152.72, which included one sample of 278 17 and the remainder below 20; non-significant studies: mean = 62.2; SD = 16.35). Interestingly, the interventions for non-significant studies were more likely to be for longer (significant studies: mean =
0.15 yrs (SD = 0.00); with one not given; non-significant studies: mean = 0.88 yrs (SD =
0.48); with one other at least 7 months duration35). None of the significant studies included an exercise component, whereas two of the non-significant studies did22, 27.
Finally, only one significant study involved groups17, while two of the non-significant studies involved groups22, 35.
Protein
There were four significant studies19, 21, 26, 27 and two non-significant studies18, 22 which measured protein. One study19 compared participants on high protein (40% carbohydrate, 30% protein, 30% fat) and high carbohydrate (55% carbohydrate, 15% protein, 30% fat) diets, and found that the high carbohydrate group had significantly lower intake of protein than the high protein group. Another significant study21 was specifically aimed at fat and carbohydrate intake, giving advice on portion size, new foods and menus. It found that both the intervention and control (standard treatment) groups had a significantly higher intake of protein (as a percentage of energy intake) at the end of the study period, and that the intervention group had significantly higher protein intake than the control group. Another study26 had specific targets for the proportions of carbohydrate, protein and fat in the diet. It found a significant increase in the intake of protein, although there was no control group to compare this result with. A further study27 gave out booklets which contained information on nutrition, the timing of Systematic Review of Healthy Eating Interventions and Diabetes 28 meals, eating out, reading food labels and adapting recipes. There were specific targets for intake of carbohydrates, fat and fiber, together with feedback from laboratory results and behavior modification techniques. It used a crossover design (described above in the section of fat) and the group which received the intervention first had significantly increased the intake of protein after six months. However, neither group had increased the intake of protein significantly between the sixth and twelfth month.
Mean sample size for the significant studies was 59.25 (SD = 63.90), with two studies having only 1219 and 1526 participants respectively, while for the non-significant studies the mean sample size was 74.00 (SD = 14.14). The mean duration of the significant studies was 1.20 years (SD = 1.87) but this was inflated by one study21 which lasted four years. The mean duration for the non-significant studies was 0.75 years (SD =
0.35). Two significant studies involved exercise 21, 27, as did one of the non-significant studies22. One21 of the significant studies, which also involved drugs, encouraged participants by ‘positive feedback and by educational exercise’, giving demonstrations of the immediate lowering effect of moderate physical activity on blood glucose. The other27 significant study individualized the activity and duration of exercise depending on the participant’s level of fitness and goals. One of the non-significant studies22 involved some group work, as did one of the significant studies21; the latter study also included spouses in the intervention.
Discussion
The heterogeneity of the studies considered in this review, and variety of different outcome measures made comparison between them extremely difficult. Rarely did a Systematic Review of Healthy Eating Interventions and Diabetes 29 study examine changes in learning, behavior, clinical improvement and health status, as recommended by the standards proposed by the American Association of Diabetes
Educators2, 6. Standardization of outcomes in future studies examining food and nutrition changes would make comparisons between different interventions much easier to examine.
Comparisons between successful (significant) and unsuccessful (non-significant) studies revealed some interesting differences between them, although there did not appear to be any clear patterns across the different outcomes, making it difficult to identify any clear distinctions. There was however, a tendency amongst studies measuring the outcomes of weight, fat intake, saturated fat intake, and carbohydrates for successful interventions to include an exercise dimension, and group work. It could be argued from this evidence, therefore, that the inclusion of exercise, and an element of group work in interventions designed to reduce weight and fat intake, and increase carbohydrate intake would be more successful than individualized programs, focusing on food only.
There was no clear pattern for sample size or duration of studies. However, it is interesting that studies of longer duration were more likely to be significant when measuring the outcomes of HbA1c, triglycerides, serum cholesterol, fat, saturated fat, protein and carbohydrates; whereas those of shorter duration were more likely to be significant when measuring the outcomes of weight, high density lipoproteins, low density lipoproteins, kilocalories, and fiber. Although these findings should be treated Systematic Review of Healthy Eating Interventions and Diabetes 30 with caution, as one study lasting four years21 will have raised the mean values of some of the significant studies, they are interesting, as they may reflect differences in the outcome variables measured. For example, the finding that studies were more likely to find interventions to be successful in reducing serum cholesterol if they were of longer duration, may suggest that changes in cholesterol are more likely to be detected over longer periods of time, and that any study seeking to do so, should consider a longer follow-up period. On the other hand, studies which examined interventions seeking to change weight and fiber intake were more likely to be successful if they were of shorter duration, suggesting that these outcomes may be more difficult to maintain over a longer period. These findings lead us to stress that the importance of future research is not only to develop interventions to promote dietary change, but also to focus on the maintenance of healthy eating behaviors3, 36.
Although there wasn’t a straightforward relationship between a study being significant and the sample size, many studies were very underpowered and would have needed beyond a large effect size to have achieved statistical significance. It is becoming increasingly recognized that if statistical significance is to be used as a means to evaluate the outcome of a study then an appropriate sample size needs to be chosen in order to give the study sufficient statistical power. Accordingly, there should be a more consistent use of power analysis at the design stage. An important element in choosing an appropriate sample size is the effect size37. Researchers could decide what would be the minimum effect that would be clinically useful and use that in their power calculations. Additional improvements which could be made in future studies would be Systematic Review of Healthy Eating Interventions and Diabetes 31 for more consistent use of randomized allocation and inclusion of a control condition.
Without these, confidence in the efficacy or lack of efficacy of a given intervention is undermined.
Before concluding, it is important to be aware of the particular aims of this review and therefore of the limits on generalization of the findings. One potential limitation is due to the search terms used in this review. The review was carried out to examine interventions which have been designed to promote healthy eating in people with diabetes, hence search terms were chosen accordingly. However, it is possible that with alternative search terms, the searches would have revealed different studies.
Secondly, although past reviews, meta-analyses and practice guidelines were used as important background information for this review, they were not used as sources of potentially eligible studies. It is possible that this may have led to the omission of some relevant studies, and this should therefore be a consideration before drawing any conclusions from the results from this review. Finally, due to considerable size of the topic of healthy eating and diabetes, the decision was made to focus on the different mechanisms of the dietary interventions, (rather than on differences between prescribed diets), and therefore studies were only included in this review if they contained some type of individualized assessment. A further systematic review of interventions comparing specific diets would be useful in providing important additional knowledge of the self-care behavior of healthy eating for people with diabetes.
In conclusion, this review demonstrates that although numerous studies have been Systematic Review of Healthy Eating Interventions and Diabetes 32 designed to examine the efficacy of dietary interventions in changing healthy eating behaviors, the diversity of intervention types and outcome measures make them difficult to compare. The quality of future research would be improved by ensuring sample sizes are adequate to give sufficient power, and also by ensuring outcomes in all four areas of learning, behavior, clinical improvement and health status2, 6 are measured.
Quality would also be improved by ensuring studies last over a period of months, rather than weeks, to ensure that potential changes in both behavior and clinical outcomes are detected. Finally, the fact that some outcome variables were less likely to show significant changes in studies of longer duration would indicate that there is clearly a need to design interventions which not only focus upon the initiation of behavior change, but also importantly, its maintenance.
Acknowledgments
We would like to express our thanks to Professor Jim Fain and Dr Sue Boren for kindly helping us to retrieve a number of the articles. Systematic Review of Healthy Eating Interventions and Diabetes 33
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13. Glasgow RE, Toobert DJ, Hampson SE. Effects of a brief office-based intervention to facilitate diabetes dietary self-management. Diabetes Care. 1996;19:835-842.
14. Glasgow RE, Toobert DJ, Hampson SE, Strycker LA. Implementation, generalization and long-term results of the “choosing well” diabetes self-management intervention. Patient Educ Couns. 2002;48:115-122.
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16. Keyserling TC, Samuel-Hodge CD, Ammerman AS et al. A randomized trial of an intervention to improve self-care behaviors of African-American women with type 2 diabetes: impact on physical activity. Diabetes Care. 2002;25:1576-83.
17. Tan AS, Yong LS, Wan S, Wong ML. Patient education in the management of diabetes mellitus. Singapore Med J. 1997;38:156-160.
18. Laitinen JH, Ahola IE, Sarkkinen ES, Winberg RL, Harmaakorpi-Iivonen PA, Uusitupa MI. Impact of intensified dietary therapy on energy and nutrient intakes and fatty acid composition of serum lipids in patients with recently diagnosed non-insulin- dependent diabetes mellitus. J Am Diet Assoc. 1993;93:276-83.
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Figure 1: Profile summarizing trial flow
Potentially relevant abstracts identified and screened for retrieval (N=497) Articles excluded as did not fulfil inclusion criteria (N=369; see text for details) Full articles retrieved for more detailed evaluation (N=86)1
Articles excluded as did not fulfil inclusion criteria (N=61; see Appendix for details) Potentially appropriate articles to be included in the systematic review (N=25) Articles excluded from final review as did not fulfil inclusion criteria (N=2; see text for Articles included in details) systematic review (N=23)
Articles withdrawn as reporting results from same sample as other Articles with useable papers already included information (N=20) (N=3)
1This number is smaller than the total number of articles meeting the inclusion criteria (N=128), due to overlap of articles across databases. Systematic Review of Healthy Eating Interventions and Diabetes 38
Table 1: Table showing outcomes measured, with the number of studies with a
statistically significant result indicated
Number Type of outcome Specific measure with statistically significant result/ number of studies assessing it
Learning Knowledge Diabetes knowledge 2/2 Nutrition knowledge 1/1 Knowledge of complications 1/1 Knowledge of control/self-care 1/1 Behavior change Nutrient intake Fat 10/14 Kilocalories, kilojoules, megajoules 5/11 a Saturated fat 7/10 Carbohydrates 5/8 a Fiber 3/8 Protein 4/6 Monounsaturated fat 2/5 Cholesterol 1/5 Polyunsaturated fat 2/4 Sucrose 1/4 Fruit and vegetables 3/3 Sodium 2/3 Soluble fiber 1/2 Potassium 0/2 Polyunsaturated fat: saturated fat 1/1 Systematic Review of Healthy Eating Interventions and Diabetes 39
Calcium 0/1 dietary behavior Dietary/food habits 3/3 Dietary self-care 1/2 Consumption of green foods 1/1 Adherence to Mediterranean diet 1/1 Fat and fiber intake 1/1 Diabetes self-care 1/1 Stage of change 1/1 Social support for diet 1/1 Dietary change 1/1 Dietary deviations 1/1 Dietary screen for high fat intake 0/1 Poor dietary practices 0/1 Clinical Improvement Non invasive physical Weight 4/13b Diastolic blood pressure 3/5b BMI 2/5 Systolic blood pressure 2/5 Body fat 1/1 Waist to hip ratio 0/1 Fat free body mass 0/1 Internal physiological/ biochemical HbA1c 8/17a Serum cholesterol 4/13a HDL cholesterol 4/9 Triglycerides 3/8 Fasting blood glucose/ daily mean blood 5/6 glucose level LDL cholesterol 2/6 High density lipoprotein to overall cholesterol 0/2 ratio Malondialdehyde 1/1 Basal free fatty acid levels 1/1 Insulin-stimulated glucose uptake 1/1 Systematic Review of Healthy Eating Interventions and Diabetes 40
Insulin suppression of endogenous glucose 0/1 production Serum creatinine 0/1 Fructosamine 0/1 Basal serum insulin levels 0/1 Blood urea nitrogen levels 0/1 C-peptide concentrations 0/1 VLDL cholesterol 0/1 Total ketones 0/1 Improved health status Integration of diabetes into daily life 2/2 Psychological well-being 0/2 Acute care visits 1/1 Diabetes intrusiveness 1/1 Diabetes-related distress 1/1 Hospital length of stay 0/1 Social well-being 0/1 Depression 0/1 aOne of the significant studies showed inconsistent results (see text for details). bPlease note that one of these significant studies was significant at the 0.05 level, but not in the desirable direction. Systematic Review of Healthy Eating Interventions and Diabetes 41
Appendix
List of articles retrieved showing those which were included in the final review and
reasons for exclusion of those which were not.
aAgurs-Collins TD, Kumanyika SK, Ten Have TR, Adams-Campbell LL. A randomized controlled trial of weight reduction and exercise for diabetes management in older
African-American subjects. Diabetes Care. 1997;20:1503-1511.
ceAlbisser AM, En Chao SC, Parson ID, Sperlich M. Information technology and home glucose clamping. Diabetes Technol Ther. 2001;3:377-86.
ceAlbisser AM, Harris RI, Sakkal S, Parson ID, Chao SC. Diabetes intervention in the information age. Med Inform (Lond). 1996;21:297-316. Erratum in: Med Inf (Lond)
1997;22:205.
cdeiAnderson EJ, Richardson M, Castle G, et al. Nutrition interventions for intensive therapy in the Diabetes Control and Complications Trial. The DCCT Research Group.
J Am Diet Assoc. 1993;93:1104.
aAnderson-Loftin W, Barnett S, Bunn P, et al. Soul food light: culturally competent diabetes education. Diabetes Educ. 2005;31:555-563.
aAnderson-Loftin W, Barnett S, Sullivan P, Bunn PS, Tavakoli A. Culturally competent Systematic Review of Healthy Eating Interventions and Diabetes 42 dietary education for southern rural African Americans with diabetes … including commentary by Melkus GD. Diabetes Educ. 2002;28:245-257.
mAsh S, Reeves MM, Yeo S, Morrison G, Carey D, Capra S. Effect of intensive dietetic interventions on weight and glycaemic control in overweight men with type II diabetes: A randomised trial. Int J Obes Relat Metab Disord. 2003;27:797-802.
eBarr Mazzuca K, Farris NA, Mendenhall J, Stoupa RA. Demonstrating the added value of community health nursing for clients with insulin-dependent diabetes. J Community
Health Nurs. 1997;14:211-224.
emBlaak EE, Glatz JF, Saris WH. Increase in skeletal muscle fatty acid binding protein
(FABPC) content is directly related to weight loss and to changes in fat oxidation following a very low calorie diet. Diabetologia. 2001;44:2013-7.
eBourn DM, Mann JI, McSkimming BJ, Waldron MA, Wishart JD. Impaired glucose tolerance and NIDDM: does a lifestyle intervention program have an effect? Diabetes
Care. 1994;17:1311-1319.
bBowerman S, Bellman M, Saltsman P. Implementation of a primary care physician network obesity management program. Obes Res. 2001;9:321S-325S.
cdhmCarlson A, Rosenqvist U. Diabetes care organization, process, and patient Systematic Review of Healthy Eating Interventions and Diabetes 43 outcomes: effects of a diabetes control program. Diabetes Educ. 1991;17:42-8.
eClark M, Hampson SE, Avery L, Simpson R. Effects of a brief tailored intervention on the process and predictors of lifestyle behaviour change in patients with type 2 diabetes.
Psychology, Health and Medicine. 2004;9:440-449.
eDavies MJ, Metcalfe J, Day JL, Grenfell A, Hales CN, Gray IP. Effect of sulphonylurea therapy on plasma insulin, intact and 32/33 split proinsulin in subjects with type 2 diabetes mellitus. Diabet Med. 1994;11:293-8.
eDavies MJ, Metcalfe J, Day JL, Grenfell A, Hales CN, Gray IP. Improved beta cell function, with reduction in secretion of intact and 32/33 split proinsulin, after dietary intervention in subjects with type 2 diabetes. Diabet Med. 1994;11:71-8.
mDullaart RP, Hoogenberg K, Riemens SC, et al. Cholesteryl ester transfer protein gene polymorphism is a determinant of HDL cholesterol and of the lipoprotein response to a lipid-lowering diet in type 1 diabetes. Diabetes. 1997;46:2082-2087.
eEriksson KF, Lindgarde F. Prevention of type 2 (non-insulin-dependent) diabetes mellitus by diet and physical exercise. The 6-year Malmo feasibility study. Diabetologia.
1991;34:891-8.
mEsmaillzadeh A, Tahbaz F, Gaieni I, Alavi-Majd H, Azadbakht L. Concentrated Systematic Review of Healthy Eating Interventions and Diabetes 44 pomegranate juice improves lipid profiles in diabetic patients with hyperlipidemia. J
Med Food. 2004;7:305-8.
aGaede P, Beck M, Vedel P, Pedersen O. Limited impact of lifestyle education in patients with Type 2 diabetes mellitus and microalbuminuria : results from a randomized intervention study. Diabet Med. 2001;18 :104-108
dhGalasso P, Amend A, Melkus GD, Nelson GT. Barriers to medical nutrition therapy in black women with type 2 diabetes mellitus. Diabetes Educ. 2005 ;31:719-25.
emGamsu DS, Sutton MS, Bennett L, Ward JD. The development of a psychoeducational group intervention for overweight women with type 2 diabetes mellitus: a service evaluation. Practical Diabetes International. 2002;19:43-50.
aGlasgow RE, La Chance PA, Toobert DJ, Brown J, Hampson SE, Riddle MC. Long term effects and costs of brief behavioural dietary intervention for patients with diabetes delivered from the medical office. Patient Educ Couns. 1997;32:175-184.
aGlasgow RE, Toobert DJ. Brief, computer-assisted diabetes self-management counseling: Effects on behaviour, physiologic outcomes, and quality of life. Med Care.
2000;38:1062-1073.
aoGlasgow RE, Toobert DJ, Barrera M, Strycker LA. The Chronic Illness Resources Systematic Review of Healthy Eating Interventions and Diabetes 45
Survey: Cross-validation and sensitivity to intervention. Health Educ Res. 2005;20:402-
409. aoGlasgow RE, Toobert DJ, Hampson SE. Effects of a brief office-based intervention to facilitate diabetes dietary self-management. Diabetes Care. 1996;19:835-842.
aoGlasgow RE, Toobert DJ, Hampson SE, Strycker LA. Implementation, generalization and long-term results of the “choosing well” diabetes self-management intervention.
Patient Educ Couns. 2002;48:115-122.
cdGlasgow RE, Toobert DJ, Hampson SE, Noell JW. A brief office-based intervention to facilitate diabetes dietary self-management. Health Educ Res. 1995;10:467-478.
fGlasgow RE, Toobert DJ, Mitchell DL, Donnelly JE, Calder D. Nutrition education and social learning interventions for type II diabetes. Diabetes Care. 1989;12:150-152.
cdehmGulliford MC, Mahabir D. A five-year evaluation of intervention in diabetes care in
Trinidad and Tobago. Diabet Med. 1999;16:939-945.
aHalford WK, Goodall TA, Nicholson JM. Diet and diabetes (II): A controlled trial of problem solving to improve dietary self-management in patients with insulin dependent diabetes. Psychology and Health. 1997;12:231-238.
bHampson SE, Glasgow RE, Strycker LA. Beliefs versus feelings : A comparison of Systematic Review of Healthy Eating Interventions and Diabetes 46 personal models and depression for predicting multiple outcomes in diabetes. British
Journal of Health Psychology. 2000;5:27-40.
cmHanefield M, Fischer S, Schmechel H, et al. Diabetes Intervention Study. Multi- intervention trial in newly diagnosed NIDDM. Diabetes Care. 1991;14:308-317.
emHarder H, Dinesen B, Astrup A. The effect of a rapid weight loss on lipid profile and glycemic control in obese type 2 diabetic patients. Int J Obes Relat Metab Disord.
2004;28:180-2.
bHaynes RB, Kris-Etherton P, McCarron DA, et al. Nutritionally complete prepared meal plan to reduce cardiovascular risk factors: a randomized clinical trial. J Am Diet Assoc.
1999;99:1077-83.
aJones H, Edwards L, Vallis TM et al. Changes in diabetes self-care behaviors make a difference in glycemic control: The Diabetes Stages of Change (DiSC) study. Diabetes
Care. 2003; 26:732-737.
fKaplan RM, Wilson DK, Hartwell SL, Merino KL, Wallace JP. Prospective evaluation of
HDL cholesterol changes after diet and physical conditioning for programs for patients with type II diabetes mellitus. Diabetes Care. 1985;8:343-348.
fKarlstrom B, Nydahl M, Vessby B. Dietary habits and effects of dietary advice in Systematic Review of Healthy Eating Interventions and Diabetes 47 patients with type 2 diabetes. Results from a one-year intervention study. Eur J Clin
Nutr. 1989;43:59-68.
aKeyserling TC, Samuel-Hodge CD, Ammerman AS et al. A randomized trial of an intervention to improve self-care behaviors of African-American women with type 2 diabetes: impact on physical activity. Diabetes Care. 2002;25:1576-83.
bejKnobler H, Schattner A, Zhornicki T, et al. Fatty liver – an additional and treatable feature of the insulin resistance syndrome. QJM. 1999;92:73-9.
aLaitinen JH, Ahola IE, Sarkkinen ES, Winberg RL, Harmaakorpi-Iivonen PA, Uusitupa
MI. Impact of intensified dietary therapy on energy and nutrient intakes and fatty acid composition of serum lipids in patients with recently diagnosed non-insulin-dependent diabetes mellitus. J Am Diet Assoc. 1993;93:276-83.
eLomasky SJ, D’Eramo G, Shamoon H, Fleischer N. Relationship of insulin secretion and glycemic response to dietary intervention in non-insulin-dependent diabetes. Arch
Intern Med. 1990;150:169-72.
mLu ZX, Walker KZ, Muir JG, O’Dea K. Arabinoxylan fibre improves metabolic control in people with type II diabetes. Eur J Clin Nutr. 2004;58:621-8.
bmMarkovic TP, Campbell LV, Balasubramanian S, et al. Beneficial effect on average Systematic Review of Healthy Eating Interventions and Diabetes 48 lipid levels from energy restriction and fat loss in obese individuals with or without type 2 diabetes. Diabetes Care. 1998;21:695-700.
bMau MK, Glanz K, Severino R, Grove JS, Johnson B, Curb JD. Mediators of lifestyle behavior change in native Hawaiians: Initial findings from the Native Hawaiian Diabetes
Intervention Program. Diabetes Care. 2001;24:1770-1775.
bMcCarron DA, Oparil S, Chait A, et al. Nutritional management of cardiovascular risk factors: A randomized clinical trial. Arch Intern Med. 1997;157:169-177.
aMcKay HG, Glasgow RE, Feil EG, Boles SM, Barrera M. Internet-based diabetes self- management and support: Initial outcomes from the Diabetes Network project.
Rehabilitation Psychology. 2002;47:31-48.
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Coding key a included article b results not provided for participants diagnosed with type 1 or type 2 diabetes c does not report an intervention to promote dietary change d does not measure at two time points, pre- and post- intervention e at least one outcome does not measure dietary behaviour f article not published between 1990 and present g has not been peer reviewed h is a cross-sectional study i is a review/advice/descriptive article/conference proceeding/lecture j describes an intervention which is targeted towards a group which is so specific that the extent to which the intervention can be applied to a general diabetic population is reduced. k is not in English l does not have human participants Systematic Review of Healthy Eating Interventions and Diabetes 56
m does not include some type of individualized assessment, development of a plan, and periodic reassessment between instructor(s) and participant when directing the selection of appropriate education materials and intervention. narticle was unobtainable oreports results from the same sample as another article already included in review, and hence was excluded from final analysis.