Catherine Gibbons

Appetite control and energy balance : impact of exercise

Exercise is widely regarded as one of the most valuable components of behaviour that can influence body weight and therefore help in the prevention and management of obesity. Indeed, long‐term controlled trials show a clear dose‐related effect of exercise on body weight. However, there is a suspicion, particularly fuelled by media reports, that exercise serves to increase hunger and drive up food intake thereby nullifying the energy expended through activity. Not everyone performing regular exercise will lose weight and several investigations have demonstrated a huge individual variability in the response to exercise regimes. What accounts for this heterogeneous response? First, exercise (or physical activity) through the expenditure of energy will influence the energy balance equation with the potential to generate an energy deficit. However, energy expenditure also influences the control of appetite (i.e. the physiological and psychological regulatory processes underpinning feeding) and energy intake. This dynamic interaction means that the prediction of a resultant shift in energy balance, and therefore weight change, will be complicated. In changing energy intake, exercise will impact on the biological mechanisms controlling appetite. It is becoming recognized that the major influences on the expression of appetite arise from fat‐free mass and fat mass, resting metabolic rate, gastric adjustment to ingested food, changes in episodic peptides including insulin, ghrelin, cholecystokinin, glucagon‐like peptide‐1 and Peptide YY, as well as tonic peptides such as leptin. Moreover, there is evidence that exercise will influence all of these components that, in turn, will influence the drive to eat through the modulation of hunger (a conscious sensation reflecting a mental urge to eat) and adjustments in postprandial satiety via an interaction with food composition. The specific actions of exercise on each physiological component will vary in strength from person to person (according to individual physiological characteristics) and with the intensity and duration of exercise. Therefore, individual responses to exercise will be highly variable and difficult to predict.

Role of resting metabolic rate and energy expenditure in hunger and appetite control: a new formulation

A long-running issue in appetite research concerns the influence of energy expenditure on energy intake. More than 50 years ago, Otto G. Edholm proposed that “the differences between the intakes of food [of individuals] must originate in differences in the expenditure of energy”. However, a relationship between energy expenditure and energy intake within any one day could not be found, although there was a correlation over 2 weeks. This issue was never resolved before interest in integrative biology was replaced by molecular biochemistry. Using a psychobiological approach, we have studied appetite control in an energy balance framework using a multi-level experimental system on a single cohort of overweight and obese human subjects. This has disclosed relationships between variables in the domains of body composition [fat-free mass (FFM), fat mass (FM)], metabolism, gastrointestinal hormones, hunger and energy intake. In this Commentary, we review our own and other data, and discuss a new formulation whereby appetite control and energy intake are regulated by energy expenditure. Specifically, we propose that FFM (the largest contributor to resting metabolic rate), but not body mass index or FM, is closely associated with self-determined meal size and daily energy intake. This formulation has implications for understanding weight regulation and the management of obesity.

Comparison of Postprandial Profiles of Ghrelin, Active GLP-1, and Total PYY to Meals Varying in Fat and Carbohydrate and Their Association With Hunger and the Phases of Satiety

CONTEXT The relationship between postprandial peptides at circulating physiological levels and short-term appetite control is not well understood. OBJECTIVE The purpose of this study was first to compare the postprandial profiles of ghrelin, glucagon-like peptide 1 (GLP-1), and peptide YY (PYY) after isoenergetic meals differing in fat and carbohydrate content and second to examine the relationships between ghrelin, GLP-1, and PYY with hunger, fullness, and energy intake. DESIGN Plasma was collected before and periodically after the meals for 180 minutes, after which time ad libitum food was provided. Simultaneous ratings of hunger and fullness were tracked for 180 minutes through phases identified as early (0-60 minutes) and late (60-180 minutes) satiety. SETTING This study was conducted at the Psychobiology and Energy Balance Research Unit, University of Leeds. PARTICIPANTS The participants were 16 healthy overweight/obese adults. MAIN OUTCOME MEASURES Changes in hunger and fullness and metabolic markers were indicators of the impact of the meals on satiety. RESULTS Ghrelin was influenced similarly by the 2 meals [F(1, 12) = 0.658, P = .433] and was significantly associated with changes in hunger (P < .05), which in turn correlated with food intake (P < .05). GLP-1 and PYY increased more by the high-fat meal [F(1, 15) = 5.099 and F(1, 14) = 5.226, P < .05]. GLP-1 was negatively associated with hunger in the late satiety phase and with energy intake (P < .05), but the PYY profile was not associated with hunger or fullness, nor was PYY associated with food intake. CONCLUSIONS The results demonstrate that under these conditions, these peptides respond differently to ingested nutrients. Ghrelin and GLP-1, but not PYY, were associated with short-term control of appetite over the measurement period.

Low Fat Loss Response after Medium-Term Supervised Exercise in Obese Is Associated with Exercise-Induced Increase in Food Reward

Objective. To examine exercise-induced changes in the reward value of food during medium-term supervised exercise in obese individuals. Subjects/Methods. The study was a 12-week supervised exercise intervention prescribed to expend 500 kcal/day, 5 d/week. 34 sedentary obese males and females were identified as responders (R) or non-responders (NR) to the intervention according to changes in body composition relative to measured energy expended during exercise. Food reward (ratings of liking and wanting, and relative preference by forced choice pairs) for an array of food images was assessed before and after an acute exercise bout. Results. 20 responders and 14 non-responders were identified. R lost 5.2 kg ± 2.4 of total fat mass and NR lost 1.7 kg ± 1.4. After acute exercise, liking for all foods increased in NR compared to no change in R. Furthermore, NR showed an increase in wanting and relative preference for high-fat sweet foods. These differences were independent of 12-weeks regular exercise and weight loss. Conclusion. Individuals who showed an immediate post-exercise increase in liking and increased wanting and preference for high-fat sweet foods displayed a smaller reduction in fat mass with exercise. For some individuals, exercise increases the reward value of food and diminishes the impact of exercise on fat loss.

No sex difference in body fat in response to supervised and measured exercise.

UNLABELLED It is often reported that females lose less body weight than males do in response to exercise. These differences are suggested to be a result of females exhibiting a stronger defense of body fat and a greater compensatory appetite response to exercise than males do. PURPOSE This study aimed to compare the effect of a 12-wk supervised exercise program on body weight, body composition, appetite, and energy intake in males and females. METHODS A total of 107 overweight and obese adults (males = 35, premenopausal females = 72, BMI = 31.4 ± 4.2 kg·m(-2), age = 40.9 ± 9.2 yr) completed a supervised 12-wk exercise program expending approximately 10.5 MJ·wk(-1) at 70% HRmax. Body composition, energy intake, appetite ratings, RMR, and cardiovascular fitness were measured at weeks 0 and 12. RESULTS The 12-wk exercise program led to significant reductions in body mass (males [M] = -3.03 ± 3.4 kg and females [F] = -2.28 ± 3.1 kg), fat mass (M = -3.14 ± 3.7 kg and F = -3.01 ± 3.0 kg), and percent body fat (M = -2.45% ± 3.3% and F = -2.45% ± 2.2%; all P < 0.0001), but there were no sex-based differences (P > 0.05). There were no significant changes in daily energy intake in males or females after the exercise intervention compared with baseline (M = 199.2 ± 2418.1 kJ and F = -131.6 ± 1912.0 kJ, P > 0.05). Fasting hunger levels significantly increased after the intervention compared with baseline values (M = 11.0 ± 21.1 min and F = 14.0 ± 22.9 mm, P < 0.0001), but there were no differences between males and females (P > 0.05). The exercise also improved satiety responses to an individualized fixed-energy breakfast (P < 0.0001). This was comparable in males and females. CONCLUSIONS Males and premenopausal females did not differ in their response to a 12-wk exercise intervention and achieved similar reductions in body fat. When exercise interventions are supervised and energy expenditure is controlled, there are no sex-based differences in the measured compensatory response to exercise.

The biology of appetite control: Do resting metabolic rate and fat-free mass drive energy intake?

The prevailing model of homeostatic appetite control envisages two major inputs; signals from adipose tissue and from peptide hormones in the gastrointestinal tract. This model is based on the presumed major influence of adipose tissue on food intake. However, recent studies have indicated that in obese people fat-free mass (FFM) is strongly positively associated with daily energy intake and with meal size. This effect has been replicated in several independent groups varying in cultural and ethnic backgrounds, and appears to be a robust phenomenon. In contrast fat mass (FM) is weakly, or mildly negatively associated with food intake in obese people. In addition resting metabolic rate (RMR), a major component of total daily energy expenditure, is also associated with food intake. This effect has been replicated in different groups and is robust. This action is consistent with the proposal that energy requirements — reflected in RMR (and other aspects of energy expenditure) constitute a biological drive to eat. Consistent with its storage function, FM has a strong inhibitory effect on food intake in lean subjects, but this effect appears to weaken dramatically as adipose tissue increases. This formulation can account for several features of the development and maintenance of obesity and provides an alternative, and transparent, approach to the biology of appetite control.

The influence of physical activity on appetite control: an experimental system to understand the relationship between exercise-induced energy expenditure and energy intake

Investigations of the impact of physical activity on appetite control have the potential to throw light on the understanding of energy balance and therefore, upon body weight regulation and the development of obesity. Given the complexity of the landscape influencing weight regulation,research strategies should reflect this complexity. We have developed a research approach based on the concept of the psychobiological system (multi-level measurement and analysis) and an experimental platform that respects the operations of an adaptive regulating biological system. It is important that both sides of the energy balance equation (activity and diet) receive similar detailed levels of analysis. The experimental platform uses realistic and fully supervised levels of physical activity, medium-term (not acute) interventions, measurement of body composition, energy metabolism (indirect calorimetry), satiety physiology(gut peptides), homeostatic and hedonic processes of appetite control, non-exercise activity, obese adult participants and both genders. This research approach has shown that the impact of physical activity on appetite control is characterised by large individual differences. Changes in body composition, waist circumference and health benefits are more meaningful than changes in weight. Further, we are realising that the acute effects do not predict what will happen in the longer term. The psychobiological systems approach offers a strategy for simultaneously investigating biological and behavioural processes relevant to understanding obese people and how obesity can be managed. This experimental platform provides opportunities for industry to examine the impact of foods under scientifically controlled conditions relevant to the real world.

Validation of a new hand-held electronic data capture method for continuous monitoring of subjective appetite sensations.

BackgroundWhen large scale trials are investigating the effects of interventions on appetite, it is paramount to efficiently monitor large amounts of human data. The original hand-held Electronic Appetite Ratings System (EARS) was designed to facilitate the administering and data management of visual analogue scales (VAS) of subjective appetite sensations. The purpose of this study was to validate a novel hand-held method (EARS II (HP® iPAQ)) against the standard Pen and Paper (P&P) method and the previously validated EARS.MethodsTwelve participants (5 male, 7 female, aged 18-40) were involved in a fully repeated measures design. Participants were randomly assigned in a crossover design, to either high fat (>48% fat) or low fat (<28% fat) meal days, one week apart and completed ratings using the three data capture methods ordered according to Latin Square. The first set of appetite sensations was completed in a fasted state, immediately before a fixed breakfast. Thereafter, appetite sensations were completed every thirty minutes for 4h. An ad libitum lunch was provided immediately before completing a final set of appetite sensations.ResultsRepeated measures ANOVAs were conducted for ratings of hunger, fullness and desire to eat. There were no significant differences between P&P compared with either EARS or EARS II (p > 0.05). Correlation coefficients between P&P and EARS II, controlling for age and gender, were performed on Area Under the Curve ratings. R2 for Hunger (0.89), Fullness (0.96) and Desire to Eat (0.95) were statistically significant (p < 0.05).ConclusionsEARS II was sensitive to the impact of a meal and recovery of appetite during the postprandial period and is therefore an effective device for monitoring appetite sensations. This study provides evidence and support for further validation of the novel EARS II method for monitoring appetite sensations during large scale studies. The added versatility means that future uses of the system provides the potential to monitor a range of other behavioural and physiological measures often important in clinical and free living trials.This study was registered as a clinical trial by Current Controlled Trials (Registration Number - ISRCTN47291569).

Effects of once-weekly semaglutide on appetite, energy intake, control of eating, food preference and body weight in subjects with obesity

The aim of this trial was to investigate the mechanism of action for body weight loss with semaglutide.

Associations among sedentary and active behaviours, body fat and appetite dysregulation: investigating the myth of physical inactivity and obesity

Background There is considerable disagreement about the association between free-living physical activity (PA) and sedentary behaviour and obesity. Moreover studies frequently do not include measures that could mediate between PA and adiposity. The present study used a validated instrument for continuous tracking of sedentary and active behaviours as part of habitual daily living, together with measures of energy expenditure, body composition and appetite dysregulation. This cross-sectional study tested the relationship between inactivity and obesity. Methods 71 participants (81.7% women) aged 37.4 years (±14) with a body mass index of 29.9 kg/m2 (±5.2) were continuously monitored for 6–7 days to track free-living PA (light 1.5–3 metabolic equivalents (METs), moderate 3–6 METs and vigorous >6 METs) and sedentary behaviour (<1.5 METs) with the SenseWear Armband. Additional measures included body composition, waist circumference, cardiovascular fitness, total and resting energy expenditure, and various health markers. Appetite control was assessed by validated eating behaviour questionnaires. Results Sedentary behaviour (11.06±1.72 h/day) was positively correlated with fat mass (r=0.50, p<0.001) and waist circumference (r=−0.65, p<0.001). Moderate-to-vigorous PA was negatively associated with fat mass (r=−0.72, p<0.001) and remained significantly correlated with adiposity after controlling for sedentary behaviour. Activity energy expenditure was positively associated with the level of PA and negatively associated with fat mass. Disinhibition and binge eating behaviours were positively associated with fat mass (r=0.58 and 0.47, respectively, p<0.001). Conclusions This study demonstrated clear associations among objective measures of PA (and sedentary behaviour), energy expenditure, adiposity and appetite control. The data indicate strong links between physical inactivity and obesity. This relationship is likely to be bidirectional.