Reviews/Commentaries/ADA Statements CONSENSUS STATEMENT Physical Activity/Exercise and Type 2 Diabetes A consensus statement from the American Diabetes Association 1,2,3 5 RONALD J. SIGAL, MD, MPH CARMEN CASTANEDA-SCEPPA, MD, PHD larger extent than exercise volume (r ϭ 2,3 6 GLEN P. KENNY, PHD RUSSELL D. WHITE, MD Ϫ0.46, P ϭ 0.26). These results provide 4 DAVID H. WASSERMAN, PHD support for encouraging type 2 diabetic individuals who are already exercising at moderate intensity to consider increasing or decades, exercise has been consid- the progression from IGT to diabetes (5). the intensity of their exercise in order to ered a cornerstone of diabetes man- Therefore, there is firm and consistent ev- obtain additional benefits in both aerobic F agement, along with diet and idence that programs of increased physi- fitness and glycemic control. medication. However, high-quality evi- cal activity and modest weight loss reduce dence on the importance of exercise and the incidence of type 2 diabetes in indi- fitness in diabetes was lacking until recent viduals with IGT. PHYSICAL ACTIVITY, years. The present document summarizes AEROBIC FITNESS, AND the most clinically relevant recent ad- EFFECTS OF STRUCTURED RISK OF CARDIOVASCULAR vances related to people with type 2 dia- EXERCISE INTERVENTIONS AND OVERALL MORTALITY — betes and the recommendations that ON GLYCEMIC CONTROL Large cohort studies have found that follow from these. Our recently published AND BODY WEIGHT IN higher levels of habitual aerobic fitness technical review on physical activity/ TYPE 2 DIABETES — Boule´ et al. and/or physical activity are associated exercise and type 2 diabetes (1) includes (6) undertook a systematic review and with significantly lower subsequent car- greater detail on individual studies, on meta-analysis on the effects of structured diovascular and overall mortality (8–10), prevention of diabetes, and on the physi- exercise interventions in clinical trials of to a much greater extent than could be Ն explained by glucose lowering alone. For ology of exercise. 8 weeks duration on HbA1c (A1C) and The present statement focuses on body mass in people with type 2 diabetes. example, Church et al. (8) found that men type 2 diabetes. Issues primarily germane Postintervention A1C was significantly in the lowest, second, and third quartiles to type 1 diabetes will be covered in a lower in exercise than control groups of cardiorespiratory fitness had 4.5-, 2.8-, subsequent technical review and ADA (7.65 vs. 8.31%, weighted mean differ- and 1.6-fold greater risk for overall mor- Statement. The levels of evidence used are ence Ϫ0.66%; P Ͻ 0.001). In contrast, tality than men in the highest quartile of defined by the ADA in ref. 2. postintervention body weight did not dif- cardiorespiratory fitness, even after ad- fer between the exercise and control justment for age, examination year, base- PHYSICAL ACTIVITY AND groups. Meta-regression confirmed that line cardiovascular disease (CVD), PREVENTION OF TYPE 2 the beneficial effect of exercise on A1C hypercholesterolemia, hypertriglyceride- DIABETES — Two randomized trials was independent of any effect on body mia, BMI, hypertension, parental CVD, each found that lifestyle interventions in- weight. Therefore, structured exercise smoking, and baseline fasting glucose lev- cluding ϳ150 min/week of physical ac- programs had a statistically and clinically els. Essentially all of the association be- tivity and diet-induced weight loss of significant beneficial effect on glycemic tween higher BMI and higher mortality 5–7% reduced the risk of progression control, and this effect was not primarily was explained by confounding with car- from impaired glucose tolerance (IGT) to mediated by weight loss. A subsequent diorespiratory fitness; there was no differ- type 2 diabetes by 58% (3,4). A cluster- meta-analysis by the same authors (7) ence in mortality among normal-weight, randomized trial found that diet alone, showed that exercise intensity predicted overweight, and obese men after adjust- exercise alone, and combined diet and ex- postintervention weighted mean differ- ment for cardiorespiratory fitness. ercise were equally effective in reducting ence in A1C (r ϭϪ0.91, P ϭ 0.002) to a In the same cohort, it was shown that ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● among moderately fit subjects (21st– 60th percentile for age) whose only exer- From the 1Department of Medicine, University of Ottawa, Ottawa, Ontario, Canada; the 2School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada; the 3Clinical Epidemiology Program, Ottawa cise was walking, the mean time spent per Health Research Institute, Ottawa, Ontario, Canada; the 4Department Of Molecular Physiology and Bio- week on exercise was 130 min for men physics, Vanderbilt University, Nashville, Tennessee; the 5Jean Mayer USDA Human Nutrition Research and 148 min for women (11). These times Center on Aging, Tufts University, Boston, Massachusetts; and the 6Department of Community and Family are consistent with recommendations Medicine, Truman Medical Center-Lakehead, University of Missouri-Kansas City School of Medicine, Kansas from the U.S. Surgeon General (12) and City, Missouri. Address correspondence and reprint requests to Ronald J. Sigal, Clinical Epidemiology Program, Ottawa other respected bodies (13–15) stating Health Research Institute, 1053 Carling Ave., Ottawa, Ontario, Canada K1Y 4E9. E-mail: [email protected]. that 150 min/week of moderate-intensity Abbreviations: CAD, coronary artery disease; CVD, cardiovascular disease; ECG, electrocardiogram; exercise should be accumulated. Moder- IGT, impaired glucose tolerance. ately fit subjects whose only exercise was A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion factors for many substances. jogging or running reported a mean of 90 DOI: 10.2337/dc06-9910 min/week for men and 92 min/week for © 2006 by the American Diabetes Association. women. These times are consistent with DIABETES CARE, VOLUME 29, NUMBER 6, JUNE 2006 1433 Exercise in type 2 diabetes an alternative and equally valid recom- obese people often have difficulty per- sus no significant change in control mendation for 30 min of vigorous activity forming sufficient exercise to create a subjects. One of these trials had a second three times a week. large energy deficit, and it is relatively phase (months 7–12), where training was To our knowledge, no meta-analysis easy to counterbalance increased energy home based rather than facility based of the effects of exercise training on lipids expenditure through exercise by eating (34). Body composition changes were or blood pressure in people with diabetes more or becoming less active outside of maintained, but exercise intensity and ad- has been published. In the general, pre- exercise sessions (22). However, in a ran- herence were lower than in the first 6 dominantly nondiabetic population, the domized trial, high-volume aerobic exer- months and the A1C difference between effects of exercise training on blood pres- cise (700 kcal/day, ϳ1 h/day of moderate- groups became statistically nonsignifi- sure (16) and lipids (17) are relatively intensity aerobic exercise) produced at cant. Other published studies of modest. Greater increases in HDL choles- least as much fat loss as the equivalent resistance exercise in type 2 diabetic par- terol and decreases in plasma triglycerides degree of caloric restriction and with ticipants have used less intense exercise have been seen with exercise programs greater resulting improvements in insulin regimens (35–40). All showed beneficial that are more rigorous in terms of both sensitivity (23). effects of the resistance exercise program volume and intensity than those that have The optimal volume of exercise to but to a lesser extent than the Dunstan et been evaluated in diabetic subjects (18). achieve sustained major weight loss is al. (32) and Castaneda et al. (33) trials. Potential mechanisms through which ex- probably much larger than needed to ercise could improve cardiovascular achieve improved glycemic control and health were reviewed by Stewart (19). cardiovascular health. In observational Safety of resistance training These include decreased systemic inflam- studies (24–27), individuals who suc- Some medical practitioners have con- mation, improved early diastolic filling cessfully maintain large weight loss over cerns about the safety of higher-intensity (reduced diastolic dysfunction), im- at least a year have typically performed resistance exercise in middle-aged and proved endothelial vasodilator function, ϳ7 h/week of moderate- to vigorous- older people who are at risk of CVD. Of- and decreased abdominal visceral fat intensity exercise. Two randomized trials ten, the main concern is that the acute accumulation. found that higher exercise volumes rises in blood pressure associated with (2,000 and 2,500 kcal/week) produced higher-intensity resistance exercise might FREQUENCY OF EXERCISE —The greater and more sustained weight loss be harmful, possibly provoking stroke, U.S. Surgeon General’s report (12) rec- than lower exercise volumes (1,000 kcal/ myocardial ischemia, or retinal hemor- ommended that most people accumulate week) (28,29). rhage. We have found no evidence that Ն30 min of moderate-intensity activity Because of the increased evidence for resistance training actually increases on most, ideally all, days of the week. health benefits from resistance training these risks. No serious adverse events However,