The impact of dietary restraint and moderate-intensity exercise on post-exercise energy intake in sedentary males

Eating Behaviors 9 (2008) 415–422

Contents lists available at ScienceDirect

Eating Behaviors

The impact of dietary restraint and moderate-intensity exercise on post-exercise energy intake in sedentary males Cristen L. Harris ⁎, Valerie A. George 1 Department of Dietetics and Nutrition, Robert Stempel School of Public Health, Florida International University, University Park, HLS 450, Miami, Florida 33199, United States

a r t i c l e

i n f o

Article history: Received 4 December 2007 Received in revised form 4 May 2008 Accepted 4 June 2008 Keywords: Dietary restraint Disinhibition Weight management Dieting Physical activity Exercise

a b s t r a c t Exercise is often used for successful weight management, particularly by males. However, exercise may have the potential to promote counter-regulatory eating, because of certain cognitive and psychological factors. The purpose of this study was to investigate the unknown role of dietary restraint, BMI, and dieting status on acute and 12-hour post-exercise energy intake (PE-EI) in sedentary males following moderate-intensity exercise. The study consisted of two experimental conditions, exercise and rest, in a counterbalanced-crossover design on two days. Exercise consisted of walking on a treadmill for 60 min. Acute and 12-hour PE-EI were compared on exercise and rest days. Eighty males, mean age 30 ± 8 years, participated in the study and were categorized by dietary restraint level, BMI, and dieting status. The main effects of condition and group, and the interaction were not significant for acute or 12-hour PE-EI, suggesting that a single bout of moderate-intensity exercise did not influence PE-EI in sedentary males in reference to dietary restraint, BMI, and dieting status. Therefore, moderateintensity exercise as a prescription for weight loss does not appear to promote counterregulatory eating in sedentary males. © 2008 Elsevier Ltd. All rights reserved.

1. Introduction According to the most recent data from the National Health and Examination Survey, the prevalence of overweight and obesity among men 20 to 60 years old has increased, to 39.7% and 31.1%, respectively (Ogden et al., 2006). This is of concern as both overweight and obesity are strongly related to an increased risk for several chronic conditions including cardiovascular disease, diabetes, high blood pressure, stroke, asthma, arthritis, certain cancers, and gallbladder disease (Mokdad, Marks, Stroup, & Gerberding, 2004). The ultimate cause of overweight and obesity is a sustained energy imbalance in which energy intake (EI) exceeds energy expenditure (EE) (Bray & Champagne, 2005). The weight loss literature suggests that “lifestyle modification,” or the combination of healthy diet, regular exercise, and behavior therapy is the foundation of obesity treatment (Fabricatore & Wadden, 2003) and successful long-term weight loss maintenance (Phelan, Wyatt, Hill, & Wing, 2006). There have been some studies that have examined the relationship between physical activity and food intake, and a few studies have specifically addressed how individuals respond to exercise in terms of food intake. A review of the effects of physical activity on food intake (Melzer, Kayser, Saris, & Pichard, 2005) indicates that acute postexercise energy intake (PE-EI) is weakly coupled with exercise-induced EE. This means that EI does not match EE for some

⁎ Corresponding author. Tel.: +1 954 818 3171; fax: +1 954 321 6563. E-mail addresses: [email protected] (C.L. Harris), georgev@fiu.edu (V.A. George). 1 Tel.: +1 305 348 2878; fax: +1 305 348 1996. 1471-0153/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.eatbeh.2008.06.004

416

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

individuals and can lead to one of two scenarios. An increase in EE due to physical activity without a corresponding increase in EI could facilitate a negative energy balance (Stubbs et al., 2002), which has beneficial implications for the role of physical activity in managing body weight. On the other hand, a decrease in physical activity resulting in a reduced EE, without a corresponding decrease in EI may lead to a positive energy balance and, ultimately, weight gain (Stubbs et al., 2004). One of the few studies that examined PE-EI in overweight males (athletes) reported a weak coupling, or undercompensation, of EI in relation to EE when moderate-intensity exercise was followed by a low fat diet manipulation (Dionne, Johnson, White, St-Pierre, & Tremblay, 1997). In this study of six young males (mean age ~ 23 years), 60 min of treadmill exercise was followed by a low fat diet, and 60 min of rest was followed by a mixed diet in a crossover design. Exercise or rest sessions concluded with a 24-hour stay in a whole body indirect calorimeter, during which time the study meals and snacks were provided. Results indicated that although the confined testing environment promoted overfeeding, fat and energy balance were significantly lower after the exercise–low fat diet condition than after the rest–mixed diet condition, demonstrating that exercise and a low fat diet can facilitate a substantial energy deficit and consequently, promote successful weight management. Studies of normal weight individuals have had varying results with regard to PE-EI. Some reports have indicated that exerciseinduced EE is compensated in the short term by a corresponding increase in EI among normal weight, physically active males (Verger, Lanteaume, & Louis-Sylvestre, 1994) and among normal weight, physically active males and females (Verger, Lanteaume, & Louis-Sylvestre, 1992). In contrast, it was recently demonstrated that relative EI was reduced following a single bout of moderateintensity cycling exercise, facilitating a short term negative energy balance among normal weight males and females (Martins, Morgan, Bloom, & Robertson, 2007). The results of some studies suggest that weight status may be a factor that influences PE-EI. Compared to their lean counterparts, it has been reported that overweight individuals are less likely to increase EI in response to an increase in EE due to physical activity (Melzer et al., 2005). However, the results of a recent study of overweight and obese sedentary males and females demonstrated considerable individual variability in weight change following a 12-week program of moderate- to high-intensity exercise, suggesting that some overweight and obese individuals who experience lower than expected weight loss do increase EI to compensate for the increase in EE (King, Hopkins, Caudwell, Stubbs, & Blundell, 2007). The results of other studies suggest that among lean, healthy males, the intensity and/or duration of exercise may be factors that influence PE-EI. In one report (King, Burley, & Blundell, 1994), participants were randomly assigned to either a resting control, low intensity, or high intensity exercise condition in the first study; and assigned to a resting control, short duration exercise, or long duration exercise (both high intensity) condition in the second study. Each condition was followed by an ad libitum test meal. Results indicated that absolute EI was not different among treatment conditions, indicating that the varying exercise protocols did not influence absolute PE-EI among lean, healthy males. Other studies have demonstrated that continuous, sub-maximal exercise for 2 h in lean, active males resulted in a higher PE-EI after exercise than after rest (Verger et al., 1992, 1994). However, the effect of exercise on PE-EI may be dose-dependent. In another study, treadmill running for 50 min twice in one day in lean, active males had no effect on absolute PE-EI on the same day or the day after (King, Lluch, Stubbs, & Blundell, 1997). It has been proposed that one reason for the discrepancy in the findings among studies may be that physical activity acts as a disinhibitor in some adults (Hill, Melby, Johnson, & Peters, 1995). In other words, a bout of exercise or physical activity may lead some individuals to relinquish control over food intake, resulting in overeating. The term disinhibition is often used in relation to dietary restraint, which has been defined as the deliberate, conscious control over food intake in order to lose body weight or prevent weight gain (King, 1999). It has been suggested that factors such as current dieting status (Hill et al., 1995) may also influence an individual's PE-EI. For example, it may be that some restrained, overweight individuals alternate between periods of restraint and disinhibition, and maintain or decrease PE-EI based on current dieting status (Hill et al., 1995). Therefore, some individuals may be unable to successfully manage their body weight due to certain psychological and cognitive factors that trigger them to overeat after participating in exercise. If this is true, it would mean that these individuals may not be able to use exercise effectively as a weight management tool without understanding their behavioral response to exercise. While the relationship between physical activity, psychological and cognitive factors, dieting status, and PE-EI has been studied to some extent in women (Visona & George, 2002; George & Morganstein, 2003), less is known about how these factors influence PE-EI in males. This is a particularly relevant topic with regard to males in that it has been reported that males are more likely to use physical activity specifically for weight control than females (Weiss, Galuska, Khan, & Serdula, 2006). In order to understand more about these issues a study was designed to investigate the relationship between weight status, dietary restraint, and dieting status on PE-EI acutely (lunch) and during the 12 h following exercise in sedentary males. The following differences in PE-EI between exercise and resting conditions among the groups were hypothesized: a) overweight males with high restraint and categorized as dieting would become disinhibited by exercise and would, therefore, have a significantly greater PE-EI than those with high or low restraint who were not dieting at the time of the study; and b) normal weight males with low restraint would have a significantly higher PE-EI than normal weight males with high restraint. 2. Methods 2.1. Participants Participants were recruited from the student, faculty and staff population at a large, urban university in South Florida. Announcements for recruitment were sent out through flyers and e-mail messages explaining that participants were needed for an

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

417

“Exercise and Eating Study.” The incentives provided included two days of free lunch and a small monetary compensation ($10). The participants were pre-screened for eligibility through a telephone interview. Eligibility criteria included: male; 21 to 45 years of age; normal weight (BMI 20.0 to 24.9 kg/m2) or overweight (BMI 25.0 to 29.9 kg/m2); nonsmoker; healthy (no known chronic disease); not taking any medications that could alter food intake; ambulatory; and regular breakfast by 9 AM/5 days per week. In addition, all participants had to be physically inactive, which was defined as having participated in b30 min of exercise twice per week or less over the past 6 months. Eighty-two percent of the individuals who responded to the recruitment ads met the eligibility criteria and were invited to participate in the study. All enrolled participants completed the study. The study was approved by the university's Institutional Review Board and all participants signed an informed consent. 2.2. Experimental design This study was designed to evaluate the effects of a single bout of moderate-intensity exercise on acute PE-EI and 12-hour EI in sedentary males. The experimental study consisted of two conditions, exercise and resting control, with each subject participating in each condition in a counterbalanced-crossover design, on two different days, four to seven days apart. The participants were randomly assigned to either an exercise or resting condition on the first day of the experiment, and then the condition was reversed on the second day. To examine the roles of dietary restraint, and dieting and weight status on PE-EI, participants were identified and assigned to one of five groups (N = 16 per group) to represent the different categories for these variables: 1) normal weight, low-restraint, non-dieting; 2) normal weight, high-restraint, non-dieting; 3) overweight, low-restraint, non-dieting; 4) overweight, high-restraint, non-dieting; and 5) overweight, high-restraint, dieting. Participants were categorized according to their body mass index, or BMI (kg/m2), and responses to the study questionnaires below. 2.3. Assessment measures At the first session, each participant completed the informed consent and study questionnaires. In addition, height and weight were measured to determine BMI (kg/m2). The investigator measured participants' weight to the nearest 0.1 kg (dressed in light clothing without shoes) using a calibrated balance-beam scale; height was measured to the nearest 0.1 cm. 2.3.1. Three-Factor Eating Questionnaire Dietary restraint was determined using the restraint scale of the Three-Factor Eating Questionnaire, or TFEQ, which is a 51-item (36 true or false, 15 multiple-choice) questionnaire used to measure three dimensions of eating behavior: 1) cognitive restraint, 2) disinhibition, and 3) susceptibility to hunger (Stunkard & Messick, 1985). Possible scores on the restraint scale range from 0 to 21, where ŒN7 is considered “high” restraint for males (Tepper, Trail, & Shaffer, 1996). The validity and reliability of this questionnaire has been established (Gorman & Allison, 1995). 2.3.2. Current dieting status Participants were asked if they were “currently dieting,” defined as “consciously trying to lose weight at this time.” This question was used in a previously published study (Visona & George, 2002). 2.4. Procedures Participants ate their typical breakfast meal at the same time on each experimental day, and then arrived (individually) at the lab between 10 and 10:15 a.m. On the exercise day, participants walked on a treadmill (Life Fitness model 90T, Schiller Park, IL) at 60–65% age-predicted maximum heart rate (220 minus age) for 60 min, which included brief periods for warming up (2 min) and cooling down (3 min). Exercise began at 10:30 a.m., and was supervised by the study investigator. Heart rate was monitored (Polar Pacer, Polar Electro Inc., Port Washington, NY) to ensure that the target heart rate was maintained. On the rest day, participants followed the same procedure as on the exercise day, except that they were asked to sit quietly for 60 min rather than exercise, during which time they could read or study. A 16.9 fl. oz. bottle of drinking water was provided to each participant at the beginning of each experimental condition, and total water intake (pre- to post-exercise or rest) was calculated. After the experimental session, each participant walked with the investigator (a 3–5 min walk) to the university cafeteria. The investigator invited the participant to choose their lunch meal (ad libitum) from the various kiosks at this facility, which offered standard menus that included a wide variety of both hot and cold foods and beverages. Individual items such as sodas, chips, candy bars, cookies, energy bars, ice cream, etc., were also available. Participants started to eat their lunch approximately 15 min after the completion of each experimental session. 2.5. Assessment of post-exercise energy intake (PE-EI) 2.5.1. Assessment of lunch PE-EI Participants were then accompanied by the investigator (a 3–5 min walk) to the university cafeteria, where various kiosks offered standard menus that included a wide variety of hot and cold foods and beverages. Participants selected their lunch meal (ad libitum) and started to eat approximately 15 min after the completion of each experimental session. It has been reported that meals eaten in the presence of other individuals are larger compared to meals eaten alone, regardless of the relationship of the eating

418

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

Table 1 Descriptive characteristics of participants Experimental group

BMI (kg/m2)

Age (years)

NW–LR–ND NW–HR–ND OW–LR–ND OW–HR–ND OW–HR–DI

Restraint score

Mean

SD

Mean

SD

Mean

SD

28 28 30 32 33

6 6 8 8 10

22a 23a 27b 28b,c 29c

2 1 2 2 1

3a 10b 3a 9b 11b

2 3 2 3 3

Note. N = 16 per group. Abbreviations: NW, normal weight; OW, overweight; LR, low restraint; HR, high restraint; ND, non-dieting; DI, dieting; SD, standard deviation. a–c Means in columns with different superscripts were significantly different according to Fisher's least significant difference post hoc test, p b .05.

companion to the participant (De Castro, 1994). Therefore, participants were asked to eat alone. The cafeteria area is large, approximately 4000 ft2, and divided into different sections. Although the investigator was present, the investigator was not in view of the participant and was seated in a separate area of the cafeteria. Participants were told where to find the investigator, and were instructed to return their meal tray to the investigator when they finished eating. This method of evaluating PE-EI has been used in a previously published study (Visona & George, 2002). After the participants exited the cafeteria, identical menu items were purchased and information concerning portion sizes was obtained from cafeteria personnel. The investigator then took any of the participant's unconsumed meal items to the laboratory for the assessment of plate waste to ultimately determine actual EI. Weights of meal items were recorded on a digital scale to the nearest 0.1 g (Denver Instrument Co. model TR-4101, Denver, CO). Nutritional analyses were performed using Food Processor SQL Edition software (version 9.6.1, 2004, ESHA Research, Salem, Oregon). 2.5.2. Assessment of 12-hour PE-EI The assessment of EI over a 12-hour period included calories consumed at the lunch meal plus everything the participants ate until midnight on each experimental day. The investigator conducted a 12-hour dietary recall by telephone the day after each experimental session. Dietary recall has been shown to be a valid method of assessing EI (Bogle et al., 2001). 2.6. Statistical analyses All statistical analyses were performed using the Statistical Package for the Social Sciences (version 12.0, 2005, SPSS Inc., Chicago, IL). One-way ANOVAs were used to evaluate group differences for descriptive characteristics such as age, BMI, etc. To determine the impact of weight, level of dietary restraint, dieting status, and exercise on the major response variable, PE-EI (lunch and 12 h), a mixed-model, repeated measures, 5 × 2 ANOVA was used. The between-subjects factor was group assignment (Group 1: normal weight, low restraint, non-dieting; Group 2: normal weight, high restraint, non-dieting; Group 3: overweight, low restraint, non-dieting; Group 4: overweight, high restraint, non-dieting; and Group 5: overweight, high restraint, dieting). The within-subject factor was the experimental condition (exercise vs. rest). For significant effects, post hoc comparisons of means were carried out using Fisher's least significant difference test. Planned, a priori contrasts in the ANOVA were used to analyze differences by weight, restraint level, dieting status, experimental condition, and their interactions. A probability level of p b .05 was selected as the criterion for statistical significance for all tests. A power analysis determined that a total of 80 males (16 subjects per cell) were necessary to detect a large effect size (f = 0.4) with 81% power and alpha= .05 in a 5 × 2 ANOVA for differences (223 kcal for lunch; 426 kcal for 12-hour intake) between exercise and rest (Cohen, 1988).

Table Lunch and 12-hour post-exercise energy intake (PE-EI) for exercise (EX) and rest days Experimental group

NW–LR–ND NW–HR–ND OW–LR–ND OW–HR–ND OW–HR–DI

Lunch EX PE-EI (kcal)

Lunch rest PE-EI (kcal)

12-hour EX PE-EI (kcal)

12-hour rest PE-EI (kcal)

Mean

SEM

Mean

SEM

Mean

SEM

Mean

SEM

1022 980 1084 1230 823

100 141 168 130 102

988 799 1183 1098 820

99 63 178 97 114

2271 2350 2450 2431 1946

160 222 185 252 142

2167 2083 2645 2461 1771

177 168 323 234 118

Note. For descriptive purposes, group means are shown for each condition separately; N = 16 per group. Abbreviations: NW, normal weight; OW, overweight; LR, low restraint; HR, high restraint; ND, non-dieting; DI, dieting; SEM, standard error of the mean. Results of repeated measures, 5 × 2 ANOVA for lunch PE-EI: condition, F(1, 75) = 1.29, p = .259, η2p = .02; group, F(4, 75) = 1.72, p = .154, η2p = .08; the interaction of condition by group, F(4, 75) = 1.25, p = .298, η2p = .06. Results of repeated measures, 5 × 2 ANOVA for 12-hour PE-EI: condition, F(1, 75) = 0.58, p = .448, η2p = .01; group, F(4, 75) = 2.09, p = .090, η2p = .01; the interaction of condition by group, F(4, 75) = 0.92, p = .455, η2p = .05.

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

419

3. Results 3.1. Participant characteristics Descriptive characteristics of the participants are displayed in Table 1. Eighty males, mean age 30 years (SD = 8), range 21 to 45, completed the study. The overall ethnic distribution of the sample was 38% Hispanic, 38% Caucasian, 8% African-American, and 16% Asian. As by design, there were significant differences in BMI, F(4, 75) = 60.50, p b .001, and dietary restraint score, F(4, 75) = 42.3, p b .001, among the groups. 3.2. Lunch and 12-hour PE-EI As shown in Table 2, weight, level of dietary restraint, dieting status, and condition did not significantly influence lunch or 12-hour PE-EI. However, there were significant results when calories were averaged across exercise and resting conditions using a priori contrasts, and means were compared between the dieting and non-dieting overweight participants. Specifically, among overweight participants, dieters had a significantly lower lunch PE-EI (M = 822 kcal, SEM = 113) than non-dieters (M = 1149 kcal, SEM = 80), F(1, 75) = 5.54, p = .021, η2p = .07; and dieters had a significantly lower 12-hour PE-EI (M = 1858 kcal, SEM = 184) than non-dieters (M = 2497 kcal, SEM = 130), F(1, 75) = 8.05, p = .006, η2p = .10. Results of repeated measures, 5 × 2 ANOVA using water intake as the dependent variable indicated a significant main effect of condition. Participants consumed significantly more water from pre- to post-exercise (M = 10.7 fl. oz, SEM = 0.6) compared to pre- to post-rest (M = 7.2 fl. oz., SEM = 0.7), F(1, 75) = 23.90, p b .001, η2p = .24. However, there were no significant findings for the main effect of group, or the interaction of condition by group. 4. Discussion In this study, the impact of dietary restraint, and dieting and weight status on PE-EI after a single bout of moderate-intensity exercise in sedentary males was examined. It was hypothesized that overweight males with high restraint, classified as dieting would become disinhibited by exercise and would have a significantly greater PE-EI at lunch and 12 h after exercise than those with high or low restraint who were non-dieting. In addition, it was hypothesized that normal weight males with low restraint would have a higher PE-EI than those with high restraint. Results indicated that there was not a significant effect of exercise on PE-EI either acutely (at lunch) or over 12 h in overweight or normal weight participants. Therefore, a single bout of moderate-intensity exercise did not act as disinhibitor among the dieting males. The fact that these results did not support our original hypotheses may be related to a number of issues. First of all, the observation that all the groups in this study held PE-EI constant relative to exercise may be due, in part, to the length of time of the study. Some of the literature, including a review (Melzer et al., 2005) indicates that increased EE due to short-term or acute PA is not immediately compensated for by increases in EI in both lean and obese individuals. This was demonstrated in males in other short-term studies looking at EI on the same day (King et al., 1994) as well as those evaluating EI for up to seven days (Stubbs et al., 2002). Also, the duration, intensity, and type of exercise may have been variables that influenced the results. Previous studies using normal weight, physically active males demonstrated that continuous, sub-maximal exercise (various athletic activities) of 2 h duration elicited a significantly greater EI after exercise than after rest (Verger et al., 1992, 1994). A more recent study of normal weight males and females found that 1 h of cycling at a moderate intensity also facilitated a significant increase in EI after exercise (Martins et al., 2007). In contrast, another study of lean, active males demonstrated that a high dose of exercise (treadmill running for 50 min twice in one day) did not have any significant effect on EI on the same day or the day after exercise (King et al., 1997). Another issue that may have influenced the results was the experimental setting in a “food-court” type cafeteria. Participants were instructed to select as much food and beverages as they wished to consume at that particular sitting. However, all menu items were pre-portioned by food service personnel. Some research has shown that regardless of level of dietary restraint or disinhibition, portion size significantly influences EI (Rolls, Morris, & Roe, 2002). In other words, individuals eat more when a larger portion size is either selected or served, regardless of restraint level. It is interesting to note that in this study, there was virtually no plate waste overall, giving support for the notion that many individuals eat to portion. The results of this study are in contrast to the results of a similar study (Visona & George, 2002) in which overweight females with high restraint and categorized as currently dieting had a higher 12-hour PE-EI after exercise than after rest, compared to overweight females with high and low restraint who were not dieting. The discrepancy in the results of these two studies may be related to several factors. First of all, it has been suggested that males who are currently dieting seem to be less prone to disinhibition than women (Provencher et al., 2004). Second, it has also been shown that exercise increases the sensory attractiveness of food in women (King, Snell, Smith, & Blundell, 1996). This may make food seem more appealing, enhancing females' tendency to replace the calories they have expended in exercise by increasing EI (Stout, 2007). Finally, males may have a different “perception” than females of the effort required to do moderate-intensity physical activity. In other words, their perception of the impact of this intensity of the activity may not have stimulated disinhibition. However, some studies have reported that gender has no influence on perceived exertion. One such study (Robertson et al., 2000) evaluated the effect of gender on “rating of perceived exertion” (RPE, Borg scale) for treadmill, simulated ski, and cycling exercises. When comparisons were made at both absolute and relative (% of maximal) heart rate, overall RPE was not significantly different between genders for all three exercise modes. Another study (Green, Crews, Bosak, & Peveler, 2003) that examined

420

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

gender differences in RPE during cycling and treadmill exercises had similar results in that overall RPE was not significantly different between genders. However, both of these studies involved maximal exercise protocols, and therefore, may not reflect RPE differences that may occur between genders during a sub-maximal, moderate-intensity exercise protocol such as the one utilized in both this study and in Visona and George's (2002) study. The results of this study are consistent with some portions of Hill et al.'s (1995) earlier model. Specifically, individuals with high restraint (lean and overweight) impose a conscious control over food intake, regardless of exercise or rest, and therefore, they may not respond to the increased energy demands of exercise by increasing EI. In the current study, such individuals would correspond to the high restraint, non-dieting, overweight and normal weight groups, who held PE-EI constant relative to exercise and rest, as suggested by Hill's model. Likewise, Hill et al. (1995) suggested that overweight individuals with low restraint may also hold EI constant, regardless of exercise or rest, due to reduced sensitivity to energy demands. These individuals would be similar to the overweight, low restraint, non-dieting group in this study who also held EI constant in response to exercise. These findings have positive implications for overweight, non-dieting males with high and low restraint, because they provide further support for the idea that exercise can help facilitate weight loss in the male population. This is relevant in that there was a significant increase in males in the prevalence of obesity (27.5% to 31.1%) from 1999 to 2004 (Ogden et al., 2006). Another issue in reference to Hill et al.'s (1995) model is that current dieting status may not be a dominant variable, but that a history of dieting and exercise is more important to consider in this type of investigation (Hill et al., 1995). It has been suggested by Lowe (1993) that an individual's vulnerability to overeating may be related to their history of dieting and overeating rather than their current level of dietary restraint (Lowe, 1993). An individual's dieting history could, in turn, be influenced by age since progressing age facilitates increased opportunities for weight loss attempts. Males, perhaps middle-age or older, who have had a more extensive history of dieting and exercise for weight loss (i.e., more frequent weight fluctuations) may, therefore, exhibit enhanced vulnerability to overeating and disinhibition by exercise. An important finding with regard to dieting status is that among the overweight participants, those who were dieting at the time of the study consumed significantly fewer calories at lunch and over 12 h than the other two overweight (nondieting) groups. In other words, exercise did not promote counter-regulatory eating behavior among the dieters, or an increase in EI to compensate for the calories expended, indicating that exercise of only a moderate intensity may play a beneficial role in facilitating weight loss in this population. This notion is in agreement with the results of a previous study (Lowry et al., 2000) in which participation in moderate-intensity physical activity, strengthening exercises, as well as vigorous physical activity were all associated with trying to lose weight or prevent weight gain among male and female college students. One of the challenges of investigating dietary restraint is having a measurement tool that focuses precisely on the concept of restraint. Although there are other methods to measure dietary restraint, the TFEQ was selected for this study because it contains three subscales including dietary restraint, disinhibition and susceptibility to hunger (Stunkard & Messick, 1985). The restraint subscale of the TFEQ reportedly measures the intent to diet (Williamson et al., 2007), which can be conceptualized as the intent to control food intake. This study design categorized participants according to level of dietary restraint. However, since overeating in response to a stimulus (disinhibited eating) has been observed in subjects with simultaneous high restraint and high disinhibition scores using the TFEQ (Westenhoefer, Broeckmann, Munch, & Pudel, 1994), the data were also analyzed based on high and low restraint scores with high and low disinhibition scores (using a median split of scores for disinhibition). Results of this analysis did not reveal disinhibited eating in response to exercise, even in those males with simultaneous high restraint and high disinhibition scores. Therefore, the authors feel confident that the data were evaluated in terms of an acceptable measure of both dietary restraint and disinhibition in relation to the hypothesis. It is noteworthy that the overweight, high restraint, dieting group had a higher BMI than the other groups (although not statistically different than the overweight, high restraint group that was not dieting). This finding is in agreement with another report (Bellisle et al., 2004) in which level of dietary restraint (measured by the TFEQ) was significantly associated with BMI in males. Although the dieters in the present study were not questioned with regard to how long they had been on their current diet, the higher BMI in this group may reflect a group of males who had recently decided to start dieting due to this very fact. There were several limitations to this study. First, the study design included an ad libitum lunch meal following each experimental condition. Although the setting was typical for the study population, it may not have reflected where each individual participant actually made their daily meal choices (such as bringing lunch from home). This may have influenced some participants' food selections, which could have biased the results. In addition, the nature of the sample, which was primarily college students and staff who were relatively young and responded to an advertisement, also limits the ability to generalize the findings. Finally, there may be limitations inherent to the testing measures themselves, such as dietary recall. Dietary recall has been shown to be a valid method of assessing EI (Bogle et al., 2001). However, there have been conflicting reports on whether level of dietary restraint (Ard, Desmond, Allison, & Conway, 2006; Rennie, Siervo, & Jebb, 2006) or BMI per se (Hill & Davies, 2001; Wansink & Chandon, 2006) influences the accuracy of self-reporting. Therefore, the unknown accuracy of self-reported 12-hour food intake may be a factor that influenced the results of this study. There were also several strengths of this study. To the authors' knowledge, this is the first study to investigate the influence of dietary restraint on post-exercise energy intake in males. The tool that was used to determine level of dietary restraint, the ThreeFactor Eating Questionnaire, is valid and reliable. In addition, the experimental design and protocol used in this study were similar to those of a previously published study among females (Visona & George, 2002), which facilitates the comparison of results between males and females. Finally, the protocol provided participants with a natural setting in which to select and consume the

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

421

test meal. Future studies could evaluate the influence of dietary restraint on post-exercise energy intake among habitual exercisers, or among inactive individuals using a variety of exercise protocols. In summary, an acute bout of moderate-intensity exercise did not significantly impact PE-EI in normal weight and overweight sedentary males who differed in terms of dietary restraint and dieting status. The results of this study suggest that overweight and normal weight males, regardless of restraint level or dieting status, are not at risk for overeating in response to exercise, and may use exercise as an effective tool for weight management and the prevention of weight gain. Acknowledgements The authors would like to thank Paulette Johnson for statistical support. Financial support was provided by an FIU Graduate School Dissertation Fellowship and by the FIU Office of Sponsored Research. References Ard, J. D., Desmond, R. A., Allison, D. B., & Conway, J. M. (2006). Dietary restraint and disinhibition do not affect accuracy of 24-hour recall in a multiethnic population. Journal of the American Dietetic Association, 106(3), 434−437. Bellisle, F., Clement, K., Barzic, M. L., LeGall, A., Guy-Grand, B., & Basdevant, A. (2004). The eating inventory and body adiposity from leanness to massive obesity: A study of 2509 adults. Obesity Research, 12(12), 2023−2030. Bogle, M., Stuff, J., Davis, L., Forrester, I., Strickland, E., Casey, P. H., Ryan, D., Champagne, C., McGee, B., Mellad, K., Neal, E., Zaghloul, S., Yadrick, K., & Horton, J. (2001). Validity of a telephone-administered 24-hour dietary recall in telephone and non-telephone households in the rural Lower Mississippi Delta region. Journal of the American Dietetic Association, 101(2), 216−222. Bray, G. A., & Champagne, C. M. (2005). Beyond energy balance: There is more to obesity than kilocalories. Journal of the American Dietetic Association, 105, S17−S23. Cohen, J. (1988). Statistical power analysis for the behavioral sciences, (2nd ed.) Hillsdale, NJ: Lawrence Earlbaum Associates. De Castro, J. M. (1994). Family and friends produce greater social facilitation of food intake than other companions. Physiology & Behavior, 56(3), 445−455. Dionne, I., Johnson, M., White, M. D., St-Pierre, S., & Tremblay, A. (1997). Acute effect of exercise and low fat diet on energy balance in heavy men. International Journal of Obesity and Related Metabolic Disorders, 21(5), 413−416. Fabricatore, A. N., & Wadden, T. A. (2003). Treatment of obesity: An overview. Clinical Diabetes, 21(2), 67−72. George, V., & Morganstein, A. (2003). Effect of moderate intensity exercise on acute energy intake in normal and overweight females. Appetite, 40(1), 43−46. Gorman, B. S., & Allison, D. B. (1995). Measures of restrained eating. In D. B. Allison (Ed.), Handbook of assessment methods for eating behaviors and weight-related problems: Measures, theory, and research (pp. 149−184). Thousand Oaks, CA: Sage Publications, Inc. Green, J. M., Crews, T. R., Bosak, A. M., & Peveler, W. W. (2003). Overall and differentiated ratings of perceived exertion at the respiratory compensation threshold: Effects of gender and mode. European Journal of Applied Physiology, 89, 445−450. Hill, J. O., Melby, C., Johnson, S. L., & Peters, J. C. (1995). Physical activity and energy requirements.American Journal of Clinical Nutrition, 62, 1059S−1066S (Suppl.). Hill, R. J., & Davies, P. S. (2001). The validity of self-reported energy intake as determined using the doubly labeled water technique. British Journal of Nutrition, 85(4), 415−430. King, N. A. (1999). What processes are involved in the appetite responses to moderate increase in exercise-induced energy expenditure? The Proceedings of the Nutrition Society, 58, 107−113. King, N. A., Burley, V. J., & Blundell, J. E. (1994). Exercise-induced suppression of appetite: Effects on food intake and implications for energy balance. European Journal of Clinical Nutrition, 48, 715−724. King, N. A., Hopkins, M., Caudwell, P., Stubbs, R. J., & Blundell, J. E. (2007). Individual variability following 12 weeks of supervised exercise: Identification and characterization of compensation for exercise-induced weight loss.International Journal of Obesity. doi:10.1038/sj.ijo.0803712 Sept. 11, advance online publication. King, N. A., Lluch, A., Stubbs, R. J., & Blundell, J. E. (1997). High dose exercise does not increase hunger or energy intake in free living males. European Journal of Clinical Nutrition, 51, 478−483. King, N. A., Snell, L., Smith, R. D., & Blundell, J. E. (1996). Effects of short-term exercise on appetite responses in unrestrained females. European Journal of Clinical Nutrition, 50, 663−667. Lowe, M. R. (1993). The effects of dieting on eating behavior: A three-factor model. Psychological Bulletin, 114(1), 100−121. Lowry, R., Galuska, D. A., Fulton, J. E., Wechsler, H., Kann, L., & Collins, J. L. (2000). Physical activity, food choice, and weight management goals and practices among US college students. American Journal of Preventive Medicine, 18(1), 18−27. Martins, C., Morgan, L. M., Bloom, S. R., & Robertson, M. D. (2007). Effects of exercise on gut peptides, energy intake and appetite. Journal of Endocrinology, 193, 251−258. Martins, C., Truby, H., & Morgan, L. M. (2007). Short-term appetite control in response to a 6-week exercise programme in sedentary volunteers. British Journal of Nutrition, 98(4), 834−842. Melzer, K., Kayser, B., Saris, W. H. M., & Pichard, C. (2005). Effects of physical activity on food intake. Clinical Nutrition, 24, 885−895. Mokdad, A. H., Marks, J. S., Stroup, D. F., & Gerberding, J. L. (2004). Actual causes of death in the United States, 2000. Journal of the American Medical Association, 291, 1238−1245. Ogden, C. L., Carroll, M. D., Curtin, L. R., McDowell, M. A., Tabak, C. J., & Flegal, K. M. (2006). Prevalence of overweight and obesity in the United States, 1999–2004. Journal of the American Medical Association, 295, 1549−1555. Phelan, S., Wyatt, H. R., Hill, J. O., & Wing, R. R. (2006). Are the eating and exercise habits of successful weight losers changing? Obesity, 14(4), 710−716. Provencher, V., Drapeau, V., Tremblay, A., Despres, J. P., Bouchard, C., & Lemieux, S. (2004). Eating behaviors, dietary profile and body composition according to dieting history in men and women of the Quebec Family Study. British Journal of Nutrition, 91, 997−1004. Rennie, K. L., Siervo, M., & Jebb, S. A. (2006). Can self-reported dieting and dietary restraint identify underreporters of energy intake in dietary surveys? Journal of the American Dietetic Association, 106(10), 1667−1672. Robertson, R. J., Moyna, N. M., Sward, K. L., Millich, N. B., Goss, F. L., & Thompson, P. D. (2000). Gender comparison of RPE at absolute and relative physiological criteria. Medicine and Science in Sports and Exercise, 32, 2120−2129. Rolls, B. J., Morris, E. L., & Roe, L. S. (2002). Portion size of food affects energy intake in normal weight and overweight men and women. American Journal of Clinical Nutrition, 76(6), 1207−1213. Stout, A. (2007). Fueling and weight management strategies in sports nutrition. Journal of the American Dietetic Association, 107, 1475−1479. Stubbs, R. J., Hughes, D. A., Johnstone, A. M., Horgan, G. W., King, N., & Blundell, J. E. (2004). A decrease in physical activity affects appetite, energy, and nutrient balance in lean men feeding ad libitum. American Journal of Clinical Nutrition, 79, 62−69. Stubbs, R. J., Sepp, A., Hughes, D. A., Johnstone, A. M., Horgan, G. W., King, N., & Blundell, J. (2002). The effect of graded levels of exercise on energy intake and balance in free-living men, consuming their normal diet. European Journal of Clinical Nutrition, 56, 129−140. Stunkard, A. J., & Messick, S. (1985). The three-factor eating questionnaire to measure dietary restraint, disinhibition and hunger. Journal of Psychosomatic Research, 29(1), 71−83. Tepper, B. J., Trail, A. C., & Shaffer, S. E. (1996). Diet and physical activity in restrained eaters. Appetite, 27(1), 51−64.

422

C.L. Harris, V.A. George / Eating Behaviors 9 (2008) 415–422

Verger, P., Lanteaume, M. T., & Louis-Sylvestre, J. (1992). Human intake and choice of foods at intervals after exercise. Appetite, 18, 93−99. Verger, P., Lanteaume, M. T., & Louis-Sylvestre, J. L. (1994). Free food choice after acute exercise in men. Appetite, 22, 159−164. Visona, C., & George, V. (2002). Impact of dieting status and dietary restraint on postexercise energy intake in overweight women. Obesity Research, 10(12), 1251−1258. Wansink, B., & Chandon, P. (2006). Meal size, not body size, explains errors in estimating the calorie content of meals. Annals of Internal Medicine, 145, 326−332. Weiss, E. C., Galuska, D. A., Khan, L. K., & Serdula, M. K. (2006). Weight-control practices among U.S. adults, 2001–2002. American Journal of Preventive Medicine, 31 (1), 18−24. Westenhoefer, J., Broeckmann, P., Munch, A. K., & Pudel, V. (1994). Cognitive control of eating behaviour and the disinhibition effect. Appetite, 23, 27−41. Williamson, D. A., Martin, C. K., York-Crowe, E., Anton, S. D., Redman, L. M., Han, J., & Ravussin, E. (2007). Measurement of dietary restraint: Validity tests of four questionnaires. Appetite, 48, 183−192.