Effect of Chronic Exercise on Appetite Control in Overweight and Obese Individuals

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Impact of Chronic Exercise on Appetite Control in Overweight and Obese Individuals

Catia Martins1,2, Bard Kulseng1,2, Jens F Rehfeld3, Neil A King4, and John E Blundell5

1Obesity Research Group, Department of Cancer Research and Molecular Medicine, Faculty of Medicine, Norwegian University of Science and Technology, Trondheim, Norway; 2Center for Obesity, Department of Surgery, St. Olav Hospital – Trondheim University Hospital, Trondheim, Norway; 3Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Denmark; 4Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia; 5BioPsychology Group, Institute of Psychological Sciences, University of Leeds, Leeds, United Kingdom

Accepted for Publication: 7 November 2012 ACCEPTED

Medicine & Science in Sports & Exercise® Published ahead of Print contains articles in unedited manuscript form that have been peer reviewed and accepted for publication. This manuscript will undergo copyediting, page composition, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered that could affect the content.

Overweight and Obese Individuals

Catia Martins1,2, Bard Kulseng1,2, Jens F Rehfeld3, Neil A King4 and John E Blundell5

1Obesity Research Group, Department of Cancer Research and Molecular Medicine, Faculty

of Medicine, Norwegian University of Science and Technology, Trondheim, Norway;

2Center for Obesity, Department of Surgery, St. Olav Hospital – Trondheim University

Hospital, Trondheim, Norway

3Department of Clinical Biochemistry, Rigshospitalet, University of Copenhagen, Denmark

4Institute of Health and Biomedical Innovation, Queensland University of Technology,

Brisbane, Australia

5BioPsychology Group, Institute of Psychological Sciences, University of Leeds, Leeds,

United Kingdom

Funding:

Catia Martins was supported by a PostDoctoral grant (SFRH/BPD/36940/2007) from

Fundação para a Ciência e Tecnologia (Portugal) under the 3rd European Union community

support programme. Running costs were covered by a grant from the Liaison Committee

between Central Norway Regional Health Authority and the Norwegian University of Science andACCEPTED Technology in partnership with St. Olav Hospital (Trondheim, Norway).

The authors declare that there is no conflict of interest that would prejudice the impartiality of

this scientific work. Moreover, the results of the present study do not constitute endorsement

by ACSM.

Corresponding author: Catia Martins

Obesity Research Group, Department of Cancer Research and

Molecular Medicine, Faculty of Medicine, Norwegian University

of Science and Technology, Trondheim, Norway

email: [email protected]

phone: 0047 72825358

fax: 0047 72 57 14 63

Running title: Exercise and appetite control

ACCEPTED

Purpose: The impact of exercise on body mass is likely to be partially mediated through

changes in appetite control. However, no studies have examined the impact of chronic

exercise on obestatin and cholecystokinin (CCK) plasma concentrations or the sensitivity to

detect differences in preload energy, in obese individuals. The objective of this study was to

investigate the effects of chronic exercise on: 1) fasting and postprandial plasma

concentrations of obestatin, CCK, leptin and glucose insulinotropic peptide (GIP) and 2) the

accuracy of energy compensation in response to covert preload manipulation.

Methods: 12-week supervised exercise programme in twenty-two sedentary

overweight/obese individuals. Fasting/postprandial plasma concentrations of obestatin, CCK,

leptin and GIP were assessed before and after the intervention. Energy compensation at a

test-meal 30 minutes after a high-energy (607 kcal) or a low-energy (246 kcal) preload, and

for the rest of the day (cumulative EI) was also measured.

Results: There was a significant reduction in the plasma concentration of fasting plasma GIP,

and both fasting and postprandial leptin concentrations after the exercise intervention (P<0.05

for all). No significant changes were observed for CCK or obestatin. A significant

preload*exercise interaction (P=0.011) was observed on cumulative EI and energy

compensation over the same period (-87±196 vs 68±165%, P=0.011). Weight loss (3.5±1.4

kg, P<0.0001) was not correlated with changes in energy compensation.

Conclusion: This study suggests that exercise improves the accuracy of compensation for

previous EI, independently of weight loss. Unexpectedly, and in contrasts to GIP and leptin, exercise-inducedACCEPTED weight loss had no impact on obestatin or CCK concentrations.

Keywords: cholecystokinin; obestatin; leptin; glucose insulinotropic peptide; energy

compensation

The impact of exercise on body mass is likely to be mediated not only directly, by

increasing energy expenditure, but also indirectly by modulating appetite, and subsequently

energy intake (22). A large body of evidence has accumulated over the last two decades

suggesting first, a link between inactivity and disrupted homeostatic mechanisms involved in

appetite control (16, 19, 24, 26, 32), which could contribute to positive energy balance (EB)

and obesity, and second, that exercise has the ability to ‘fine-tune’ these physiological

mechanisms (19, 23, 35). Exercise has been shown to improve energy compensation by

leading to a more sensitive eating behaviour in response to previous energy intake (EI) (21).

However, the majority of the evidence is cross-sectional (19, 35) or derived from normal-

weight individuals (231). The mechanisms whereby this occurs have yet to be clarified, but

exercise has been shown to induce changes in appetite-regulating hormones which may

contribute to a better appetite control (22).

Appetite-regulating hormones can be grouped, in a simplistic way, in two categories:

episodic signals, which are periodically released, mainly from the gastrointestinal (GI) tract,

in response to feeding or fasting, signalling acute nutritional state, and tonic signals, which

are more uniformly released, mainly by the adipose tissue, in proportion to the amount of

stored lipids, signalling chronic nutritional state (2). To the first category of peripheral GI

signals belongs ghrelin, an orexigenic hormone released in response to fasting, and several

hormones involved in satiation and/or satiety such as cholecystokinin (CCK), glucagon-like

peptide-1 (GLP-1) and polypeptide YY (PYY), which are released in response to feeding. The secondACCEPTED category of peripheral signals includes leptin, released mainly by the adipose tissue, and insulin, released by the pancreas, whose secretion is directly proportional to the

amount of fat stores. However, insulin also shows episodic characteristics since it is released

periodically in response to food consumption.

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. Obestatin and glucose insulinotropic peptide (GIP) may also be involved in appetite

control. Obestatin, a peptide encoded by the ghrelin gene, was initially shown to have

anorexigenic properties (36), however, more recent research has questioned these findings

and, at present, the real impact of obestatin on food intake and body mass regulation remains

unknown (8). GIP, is best known for its incretin action, however, accumulating evidence over

the last decade seems to suggest that GIP may also play a role in appetite control and body

mass regulation, by stimulating food intake (3, 27-30).

We have recently shown that exercise-induced weight loss, in previously sedentary

overweight and obese individuals, results in an increased drive to eat in the fasting state, with

an increase in fasting subjective hunger together with acylated ghrelin plasma concentrations

However, this increase in fasting orexigenic drive seems to be balanced by an improved

satiety response to a meal and improved sensitivity of the appetite control system. We

reported a significant suppression of acylated ghrelin following a fixed meal, which was not

present before the exercise intervention, and a tendency towards increased late postprandial

release of GLP-1 and PYY (21). However, little is known regarding the impact of chronic

exercise on other appetite-related hormones.

The aim of the present study was, therefore to examine the effect of chronic exercise

in previously sedentary overweight/obese volunteers, on: 1) fasting and postprandial plasma

concentrations of obestatin, CCK, leptin and GIP and 2) the accuracy of energy compensation

in response to covert preload manipulation.

MATERIALSACCEPTED AND METHODS Participants

Twenty-two overweight and obese healthy sedentary individuals were recruited for

this study through advertisement posted at the Norwegian University of Science and

defined as not engaged in strenuous work or in regular brisk leisure physical activity more

than once a week or in light exercise for more than 20 minutes/day on more than 3

times/week. This was assessed through an exercise history of the three months prior to the

study. Those dieting to lose weight, weight unstable on the last three months (>2kg) or with a

restraint score derived from the Three Factor Eating Behaviour Questionnaire (33) >12 were

not included in the study. Seven women did not complete the study for different reasons,

including unplanned pregnancy, injury and time constrains. Fifteen participants (8 men and 7

women), with a mean body mass index of 31.3±3.3 kg/m2 and a mean age of 36.9±8.3 years,

completed the study.

This study was conducted according to the guidelines laid down in the Declaration of

Helsinki and was approved by the regional Ethics Committee (Midt-Norge, Trondheim,

Norway). Written informed consent was obtained from all participants before enrolling in the

study. The data reported here are part of a larger metabolic study that has been published

previously (21).

Study Protocol

Participants underwent a 12-week supervised exercise programme (5 days a week)

consisting of treadmill walking or running and were asked to maintain their normal diet

throughout the study. The exercise programme was individually designed in order to induce a

500 kcal energy deficit per session at approximately 75% maximal heart rate (maxHR). Several measurementsACCEPTED were performed before and after the intervention including: body mass

and composition, maximal oxygen consumption (VO2max), resting metabolic rate, habitual

food intake, fasting and postprandial blood samples and subjective sensations of appetite. For

more details about the study methodology see Martins et al, 2010 (21). The preload test-meal

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. paradigm was also used to assess the ability of the participants to regulate their food intake in

response to preload covert manipulation.

Before and immediately after the 12-week exercise intervention (at least 48 hours

after the last exercise session to exclude acute effects of exercise), participants came to the

lab on 3 occasions: a) to measure the release of appetite-related hormones in fasting and after

a standard breakfast, b) for an appetite challenge day where a low-energy preload (LEP) was

used and c) for an appetite challenge day where a high-energy preload (HEP) was used.

These measurements are described in detail below.

Fasting and postprandial release of appetite-related hormones On each occasion an

intravenous cannula was inserted into an antecubital vein. Two fasting baseline blood samples

(-10 and 0 minutes) were taken and participants were instructed to consume a standard

breakfast (time=zero) (consisting of bread, orange juice, milk, cheese and jam: 600 kcal, 17%

protein, 35% fat, 48% carbohydrate) within 10 minutes. Blood samples were taken at 30 min

intervals for a period of 3 hours.Venous blood was collected into potassium EDTA-coated

tubes, containing 500KIU aprotinin (Pentapharm, Basle, Switzerland)/ml whole blood.

Samples were then centrifuged at 2000 g for 10 minutes and kept at –20° C for later analyses.

All samples were batch analysed at the end of the study to reduce inter-assay variability.

Obestatin and leptin were quantified using human-specific RIA kits (Phoenix

Pharmaceuticals, 330 Beach Road, Burlingame, CA, USA and Millipore, Billerica, MA,

USA, respectively), CCK using an extensively characterized “in house” RIA method (27) and GIP usingACCEPTED an ELISA kit (Millipore, Billerica, MA, USA). The sensitivity of the assays was 50 pg/ml for obestatin, 0.5 ng/ml for leptin, 0.3pmol/L for CCK and 8.2 pg/mL for GIP. All

samples were assayed in duplicate and baseline and end samples of the same individual were

analysed in the same batch. The intra-assay coefficient of variation was of <10% for all

previously concentrated by freeze drying.

B. Preload-test-meal paradigm

Using a randomized single-blind crossover design, participants consumed either a

HEP or LEP at baseline (week 0) on different days of the week (appetite challenge days), at

least two days apart in order to avoid participants from becoming bored with the pasta lunch

and to prevent any crossover effects. This was repeated after the 12-week exercise

intervention (week 13), with participants acting as their own controls.

On the morning of each appetite challenge day, participants were asked to consume

their usual breakfast before 8.00 am and to eat exactly the same type and amount of food in

each of the four “appetite challenge days”. Compliance with this recommendation was

achieved by asking each participant to describe in detail his breakfast on the first preload

session, and the researcher recording this information. On the morning of subsequent

“appetite challenge days” participants were asked what they had eaten for breakfast, to ensure

that this was the same as previous days. After the standard breakfast participants were

instructed not to eat or drink anything except water. Participants were also asked to avoid

alcohol consumption and exercise during the 24 hours prior to, and during each appetite

challenge day and to record everything they ate and drank on the day before each “appetite

challenge day”. No significant differences on 24h energy or macronutrient intake on the day

before each preload session were observed. TheACCEPTED appetite challenge days after the exercise intervention were performed at least 48 hours after the last exercise session to exclude acute effects of exercise. Subjective sensations

of hunger (“How hungry do you feel?”), fullness (“How full do you feel?”), desire to eat

(“How much would you like to eat?”) and prospective food consumption (“How much do you

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. think you can eat?”) were assessed, throughout each appetite challenge day, using 10cm self-

rated visual analogue scales (VAS) as previously described (11). Participants sat quietly after

arrival and instructions regarding the completion of the VAS were provided. The first VAS

was completed to assess baseline appetite feelings. Preloads were then presented and

participants were asked to consume them within 5 minutes. Further VAS were completed

immediately after the preload and then at 20, 40 and 60 minutes. During this period of time,

participants stayed in the Research Unit, but they were permitted to write and read. The ad

libitum lunch test-meal was served 60 minutes after the preload, and participants ate in an

individual booth and instructed to eat until comfortably full. After lunch, participants left the

unit and were instructed to record all they consumed until the end of the day in a food diary

in order to estimate cumulative energy intake over that day (lunch plus subsequent food

intake till bedtime). To facilitate and improve the accuracy of estimating portion sizes,

participants were provided with a booklet with pictures of the most commonly eaten

food/dishes in Norway (validated for the Norwegian population, with each food/dish being

presented at 4 different portions sizes). Participants were also taught how to use the booklet

and how to ensure that all food eaten was reported. Dietary analysis was performed using Mat

på Data 5.0 program (Landsforeningen for kosthold og helse, Oslo, Norway).

Two preloads with different energy contents: high- and low-energy preloads (HEP

and LEP), but similar sensory properties were used in this study. They were presented as 450

ml flavoured milkshakes differing in energy content by 361 kcal which was achieved by

adding maltodextrin to the LEP (Table 1). Food intakeACCEPTED after preload consumption was assessed using an ad libitum test-meal lunch, consisting of pasta with tomato sauce and cheese, which was provided in excess of expected

consumption (total energy and macronutrient value: 2091 kcal, 76g protein, 65g fat and 295g

carbohydrates). Food was weighed before participants ate and re-weighed after each

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. participant had finished eating, to allow calculations of energy and macronutrient intake. All

dietary analysis was performed according to manufacturers’ nutritional composition

information. Participants were presented with exactly the same type and amount of food on

all four appetite challenge days.

Statistical Analysis and treatment of data

Statistical analysis was carried out using SPSS (SPSS Inc., Chicago, IL). All variables

were checked regarding their normal distribution using the Shapiro-Wilk test. Statistical

significance was assumed at P<0.05, unless otherwise stated.

Differences in the fasting plasma concentrations of the hormones measured, before

and after the exercise intervention, were assessed by paired sample t-tests. The effect of time

and exercise (pre- versus post-intervention) on postprandial concentrations of the hormones

was assessed by a repeated-measures ANOVA.

The effect of preload (HEP vs LEP) and exercise (pre vs post) on energy intake (EI), at

the lunch test-meal and on cumulative EI over the day was assessed by a repeated-measures

ANOVA.

Energy compensation was calculated as the difference in EI at the pasta lunch (or over

the day – cumulative EI) between the two study days (HEP vs LEP) divided by the difference

in preload energy content and expressed as a percentage (13). This was labelled as the

compensation index. The area under the curve (AUC) for each subjective feeling of appetite

was calculated for a period of 1 hour (from before preload till before pasta lunch) using the trapezoidalACCEPTED rule. The effect of preload (HEP vs LEP) and exercise (pre vs post) on the AUC for each subjective feeling of appetite was assessed by a repeated-measures ANOVA.

Anthropometry and fitness level

The 12-week exercise intervention resulted in significant reductions in body mass

(96.1±11.0 to. 92.6±11.7kg, P<0.0001) and percentage of body fat (35.3±5.6 to 33.5±5.9%,

P<0.0001), and a significant increase in VO2max (32.9±6.6 to. 37.7±5.9 ml/kg/min,

P<0.0001). For more details on the impact of this exercise program on metabolism see

Martins et al, 2010 (18).

Plasma concentrations of hormones

Fasting concentrations

The fasting plasma concentrations of the hormones measured, before and after the 12-

week exercise intervention are shown in Table 2. The exercise intervention resulted in a

significant reduction in leptin and GIP fasting concentrations (t=2.51, d.f.=14, P=0.025;

t=2.83, d.f.=14, P=0.014, respectively), but no significant changes in obestatin or CCK fasting

concentrations.

Postprandial concentrations

No significant effect of time, exercise or interaction was observed on obestatin plasma

concentrations (Fig. 1a).

A significant effect of time (F(5,8)=23.7, P<0.0001), but no effect of exercise or

interaction was observed on CCK concentrations, which increased following the standard breakfast, ACCEPTEDpeaking at 90-120 min post-ingestion (Fig. 1b). A significant effect of time (F(5,10)=6.25, P<0.01) and exercise (F(1,14)=5.74,

P<0.05), but no interaction was observed on leptin concentrations, which decreased following

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. the standard breakfast, with a nadir at 60 min post-ingestion (Fig. 1c) and were lower after

the exercise intervention compared with baseline concentrations.

A significant effect of time (F(5,9)=19.85, P<0.0001), but no effect of exercise or

interaction was observed on GIP concentrations, which increased following the standard

breakfast, peaking at 90-120 min post-ingestion (Fig. 1d).

Lunch test-meal EI

EI at lunch following the LEP and HEP before and after the exercise intervention, is

shown in figure 2. ANOVA revealed a significant effect of preload on lunch EI (kcal). EI

after the LEP was significantly higher compared with the HEP (615±323 vs 545±268kcal; F

(1,13)=6.09, P<0.05). No significant effects of exercise or interaction were observed on lunch

EI. There was also no significant effect of exercise on short-term energy compensation (%) at

lunch (15.5±33.6 vs 23.4±42.0%, t=-0.63, d.f.=14, P>0.05).

Cumulative EI

There was a significant exercise x preload interaction (F(1,13)=8.89, P=0.011) on

cumulative EI, but no significant effects of exercise or preload (Figure 3) . Post-hoc analysis

revealed that, at baseline, cumulative EI after HEP was significantly higher than after the

LEP (2118±775 vs 1803±421 kcal, P=0.001), while after the 12-week exercise programme

the opposite was observed: cumulative EI after the HEP was significantly lower than after the

LEP (1799±649 vs 2044±763kcal, P=0.001). WhenACCEPTED energy compensation was calculated using cumulative EI over the day, the exercise intervention exerted a significant increase in the accuracy of compensatory

adjustment for the different preloads (pre-intervention: -87±196 vs post-intervention:

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. 68±165%, t=-2.93, d.f.=14, P=0.011). There were no significant effects of exercise, preload

or interaction on the relative (%) contribution of each macronutrient to 24 h cumulative EI.

Changes in subjective sensations of appetite

The AUC for subjective sensations of hunger, fullness, desire to eat and prospective

food consumption (before preload intake to before lunch - 60 min period) are presented in

figure 4. ANOVA showed no significant effects of exercise, preload or interaction on the

AUC of any subjective sensations of appetite.

DISCUSSION

To the best of our knowledge, this is the first study to assess the impact of chronic

supervised exercise, in overweight/obese sedentary individuals, on CCK and obestatin

secretion before and after a meal. Counter-intuitively, 12 weeks of exercise inducing an

average 3.5 kg weight loss had no significant impact on either fasting or postprandial

concentrations of CCK or obestatin in plasma, in previously sedentary overweight/obese

individuals. Previous studies on the impact of acute exercise on CCK secretion had reported

an increase in fasting (1) and postprandial concentrations in normal-weight individuals (31).

Evidence regarding the impact of chronic exercise on CCK concentrations in plasma was,

however, up to now, limited to one study showing no change in fasting CCK plasma

concentrations after a four-week exercise programme in active men (1). Regarding obestatin,

no significant changes had been described after a single bout of resistance exercise in both men (6) andACCEPTED women (7) and after six consecutive days of anaerobic exercise in normal-weight women (20).

In the present study, we also assessed changes in circulating leptin and GIP

concentrations in response to 12 weeks of exercise, in previously sedentary overweight/obese

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. individuals, and found a significant reduction in fasting GIP concentrations, and both fasting

and postprandial leptin concentrations in plasma. Studies on the impact of chronic exercise on

GIP secretion are relatively scarce. Three months of exercise in obese women were shown to

reduce both fasting and postprandial GIP concentrations in plasma (18). However, another

study in older obese adults with impaired glucose tolerance reported no change in fasting or

postprandial GIP concentrations after 12 weeks of exercise (14). This is unexpected given

that the exercise intervention employed and the magnitude of weight loss achieved were very

similar to those described in our study . It is possible that older subjects with impaired

glucose-tolerance may need a bigger stimulus to alter GIP secretion. If GIP has indeed

orexigenic properties, as previously discussed in our introduction (3, 27-29), then the

significant reduction in fasting GIP concentrations observed in the present study is not in line

with the raised fasting hunger feelings and ghrelin concentrations reported previously in

response to exercise-induced weight loss (21). It needs to be acknowledged that a recent

study (9) reported no change in either fasting hunger or acylated ghrelin after 12-weeks of

aerobic or resistance exercise inducing a significant fat mass loss. As highlighted by the

authors, lower fat mass loss, lower volume of exercise and the inclusion of only men vs men

and women compared with our study (19) are likely to have contributed to the discrepancy.

Although the impact of chronic exercise on leptin secretion has been extensively

studied and a consensus exists that exercise, when associated with fat mass loss, is generally

followed by a significant reduction in fasting leptin concentrations (17), very little is known

regarding the impact of chronic exercise on postprandial leptin secretion. The present study has shownACCEPTED that exercise-induced weight loss leads not only to a reduction in leptin concentrations in fasting, as expected, but also in the postprandial state. Leptin is the primary

adipose hormone that conveys information to the hypothalamus concerning the status of

energy stores. It helps to regulate energy homeostasis and body mass by suppressing appetite

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. and increasing energy expenditure (25). Moreover, leptin seems to be able to modulate the

responsivity to satiety signals, such as CCK (4) and has been shown to be correlated with

satiety ratings in the post-exercise period (34). The increase in hunger levels and reduction in

leptin concentrations experienced by obese individuals after weight loss were previously

shown to be correlated (10). . The reduced leptin concentration observed after chronic

exercise might reflect improved leptin transport and thus greater leptin sensitivity (34).The

second aim of this study was to examine the effect of chronic exercise on the accuracy of

energy compensation in response to covert preload energy manipulation in overweight/obese

individuals. The results suggest that exercise improves appetite control in overweight/obese

individuals by leading to a more sensitive eating behaviour in response to previous EI. These

findings confirm previous cross-sectional data reporting a more accurate energy

compensation in active versus inactive individuals (19, 35) and confirm our previous findings

in normal-weight individuals involved in a six-week exercise programme (23). These results

are also consistent with the outcome of another study showing that 12 weeks of exercise

increase the satiating effect of a fixed meal in obese individuals (15). However, in two of the

previous 3 studies (23,35), and in agreement with the findings of the present study, no

difference in energy compensation was observed at the laboratory test meal, but only after

including the self-reported measures of EI, for the remainder of the day, after leaving the

laboratory.In the present study, sedentary overweight/obese individuals, had a higher

cumulative EI after the HEP compared with after the LEP at baseline, denoting a weak

compensatory response. A 12-week exercise intervention was able to normalise that pattern, with participantsACCEPTED being able to subconsciously detect difference in preload energy content by eating less throughout the day after the HEP compared with after the LEP. Energy

compensation over the course of the day (expressed as a %) increased significantly from an

average of -87±196% at baseline to 68±165% after the exercise intervention, despite a very

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. large inter-individual response. Interestingly, this improvement in energy compensation was

not correlated with weight loss. This finding, combined with previous evidence

demonstrating improvement in energy compensation over a 24h period after exercise in

normal-weight individuals, in the absence of weight loss (23), suggests that the improvements

may be independent of weight loss.

We acknowledge that this study has some limitations. First, we did not include a no-

exercise control group and, as such, we cannot be sure that other factors, apart from exercise,

could not have played a role. Even though familiarization with the test procedure could have

played a role, pre and post-intervention testing were more than 3 months apart, making it

unlikely to have played a major role. Second, it is intriguing that the improvement in energy

compensation with exercise was only observed outside of the laboratory environment. This is

likely to be a result of the type of laboratory test meal used: pasta with tomato sauce and

cheese. It is possible that there was a delay in compensation, or that participants were better

able to compensate in their natural environment (outside of the lab). Although self-reported

diet records used to estimate EI after leaving the lab may be susceptible to inaccurate

reporting, it is unlikely that a systematic error has occurred. Energy expenditure outside of

the lab was not measured. Therefore, it is possible that compensation occurred in the form of

activity-based energy expenditure, however there is no strong evidence for this elsewhere.

Although we found no significant exercise x preload interaction on the AUC of any of the

subjective feelings of appetite assessed, a closer analysis of figure 4 reveals non-significant

patterns of change that are consistent with an improved discriminatory response between preloads withACCEPTED the exercise intervention. At baseline, AUC hunger after the HEP was higher than after the LEP (denoting an abnormal response). After the exercise intervention the effect

was reversed. A similar pattern was observed for AUC fullness. AUC for desire to eat and

prospective food consumption were very similar after each preload at baseline, whereas after

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. the exercise intervention AUCs after HEP were lower than after the LEP. The lack of

significance may be a result of the small sample size and more studies with large samples

need to be done to confirm this finding.

The question that naturally arises from the previous findings is what physiological

changes, at the level of the appetite control system, occurred with exercise that can explain

this improved discriminatory ability to differentiate between preloads with different energy

contents. GI hormones involved in short-term appetite control, such as the orexigenic

hormone ghrelin and the satiation/satiety hormones CCK, GLP-1 and PYY are potential

candidates. However, in this study we did not measure the release of these hormones after

each preload at baseline and after the 12 week exercise intervention. Other potential

candidates are via changes in substrate metabolism (12) or alteration in the neuronal

responses to food (3) in response to training.

We had previously shown that exercise-induced weight loss induces a dual effect on

appetite control by increasing the drive to eat in the fasting state (early morning), while

improving the satiating effect of a meal and the sensitivity of the appetite control system in

overweight/obese individuals (15, 21). The results of the present study showing reduced

leptin plasma concentrations in the absence of changes in fasting CCK or obestatin, and a

better compensatory response to an energy preload extend and strengthen our previous

findings. More studies are needed to completely understand the implications of reduced GIP fasting levelsACCEPTED in response to chronic exercise in the context of appetite control.

Catia Martins was supported by a PostDoctoral grant (SFRH/BPD/36940/2007) from

Fundação para a Ciência e Tecnologia (Portugal) under the 3rd European Union community

support programme. Running costs were covered by a grant from the Liaison Committee

between Central Norway Regional Health Authority and the Norwegian University of Science

and Technology in partnership with St. Olav Hospital (Trondheim, Norway).

The authors’ responsibilities were as follows: CM, NAK and JEB were involved in the

design of the study; CM was involved in data collection and statistical analysis; BK was

involved in clinical support and study implementation. JFR was responsible for the plasma

CCK measurements. All the authors were involved in manuscript writing.

We would like to thank all the participants that took part in this study for their time

and enthusiasm and Mrs. Sissel Salater and Mrs. Trude Haugen for their help with

cannulation.

The authors declare that there is no conflict of interest that would prejudice the

impartiality of this scientific work. Moreover, the results of the present study do not

constitute endorsement by ACSM. ACCEPTED

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ACCEPTED

Figure 1a. Obestatin plasma levels (ng/mL) over time after breakfast, before (♦) and after a

12-week exercise intervention (□). Values represent means ± SEM for 15 subjects. Repeated

measures ANOVA showed no significant effect of time, exercise on interaction.

Figure 1b. CCK plasma levels (pmol/L) over time after breakfast, before (♦) and after a 12-

week exercise intervention (□). Values represent means ± SEM for 15 subjects. Repeated

measures ANOVA showed a significant effect of time (P<0.0001), but no effect of exercise or

interaction.

Figure 1c. Leptin plasma levels (ng/ml) over time after breakfast, before (♦) and after a 12-

week exercise intervention (□). Values represent means ± SEM for 15 subjects. Repeated

measures ANOVA showed a significant effect of time (P<0.01) and exercise (P<0.05), but no

interaction.

Figure 1d. GIP plasma levels (pg/ml) over time after breakfast, before (♦) and after a 12-

week exercise intervention (□). Values represent means ± SEM for 15 subjects. Repeated

measures ANOVA showed a significant effect of time (P<0.0001), but no effect of exercise or

interaction.

Figure 2. Energy intake (kcal) at lunch after the high- (HEP) and low-energy preloads (LEP), before andACCEPTED after the exercise intervention (n=15). Results are expressed as mean ± SEM. ANOVA showed a significant effects of preload (P<0.05), but no effect of exercise or

interaction.

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. Figure 3. Cumulative EI after the high- (HEP) and low-energy preload (LEP), before and

after the exercise intervention (n=15). Results are expressed as mean ± SEM. ANOVA

showed a significant exercise*preload interaction (P=0.011), but no effects of exercise or

preload.

Figure 4. AUC (0-60 minutes) for subjective feelings of appetite after the high- (HEP) and

low-energy preloads (LEP), before and after the exercise intervention (n=15). Results are

expressed as mean ± SEM. ANOVA showed no significant effects of exercise, preload or

interaction on the AUC of any the subjective feeling of appetite.

ACCEPTED

Copyright © 2012 by the American College of Sports Medicine. Unauthorized reproduction of this article is prohibited. Table 1. Ingredients and nutritional composition of the low- (LEP) and high- energy (HEP) preloads Low-energy preload High-energy preload Ingredients (g): Double cream 46 46 Maltodextrin (Maxijul) 0 95 Nesquik * 10 10 Nutritional composition: Energy (kcal) 246 607 Protein (g) 0.9 0.9 Carbohydrate (g) 10.5 100.7 Fat (g) 22.2 22.2 Amounts and nutritional composition per 450 ml serving, made up to this volume with water. * chocolate, strawberry or banana flavoured

ACCEPTED

Table 2. Fasting plasma levels of obestatin, CCK, leptin and GIP at baseline and end of the exercise intervention (n=15) Baseline End Obestatin (pmol/L) 108.7±61.8 103.2±39.0 CCK (pmol/L) 1.29±1.04 1.03±0.48 Leptin (ng/ml) 17.6±10.8* 13.8±9.6* GIP (pg/ml) 49.2±25.1* 33.8±13.4* Results expressed as mean ± SD. Means sharing the same symbol denote significant differences between baseline and end: * P<0.05,

ACCEPTED