James Stubbs

Metabolic and behavioral compensatory responses to exercise interventions: barriers to weight loss.

An activity‐induced increase in energy expenditure theoretically disturbs energy balance (EB) by creating an acute energy deficit. Compensatory responses could influence the weight loss associated with the energy deficit. Individual variability in compensation for perturbations in EB could partly explain why some individuals fail to lose weight with exercise. It is accepted that the regulatory system will readily defend impositions that promote a negative EB. Therefore, a criticism of exercise interventions is that they will be ineffective and futile methods of weight control because the acute energy deficit is counteracted. Compensation for exercise‐induced energy deficits can be categorized into behavioral or metabolic responses and automatic or volitional. An automatic compensatory response is a biological inevitability and considered to be obligatory. An automatic compensatory response is typically a metabolic consequence (e.g., reduced resting metabolic rate) of a negative EB. In contrast, a volitional compensatory response tends to be deliberate and behavioral, which the individual intentionally performs (e.g., increased snack intake). The purpose of this review is to highlight the various metabolic and behavioral compensatory responses that could reduce the effectiveness of exercise and explain why some individuals experience a lower than expected weight loss. We propose that the extent and degree of compensation will vary between individuals. That is, some individuals will be predisposed to compensatory responses that render them resistant to the weight loss benefits theoretically associated with an exercise‐induced increase in energy expenditure. Therefore, given the inter‐individual variability in behavioral and metabolic compensatory responses, exercise prescriptions might be more effective if tailored to suit individuals.

Energy density of foods: effects on energy intake.

This article examines the importance of dietary energy density (ED) as a major factor that may influence human appetite and energy intake (EI). The article examines whether the effects of diet composition on appetite and EI can be explained in terms of ED. There is clear evidence that dietary macronutrients exert differential effects on energy intake (EI), both in the laboratory and in real life. Under normal conditions where fat contributes disproportionately to ED, protein, carbohydrate, and fat exert hierarchical effects on satiety in the order protein >carbohydrate > fat. Alcohol appears to stimulate EI. In human appetite studies the main effect of controlling ED is to diminish the impact of differences in the satiating effects of fat and carbohydrate. ED exerts profound effects in constraining EI in short-to-medium term studies. Subjects behave differently in longer term interventions. In short-to-medium term laboratory studies, increases in ED are more effective at increasing EI than at decreasing food intake. In longer term and cross-sectional studies conducted in naturalistic environments, increased ED appears more effective at decreasing food intake and less effective at elevating EI. The available evidence suggests that we should be evolving more complex, multifactor models to account for the observations that both macronutrients and ED affect EI rather than substituting one simplistic model with another.

Dual-process action of exercise on appetite control: increase in orexigenic drive but improvement in meal-induced satiety

BACKGROUND Exercise could contribute to weight loss by altering the sensitivity of the appetite regulatory system. OBJECTIVE The aim of this study was to assess the effects of 12 wk of mandatory exercise on appetite control. DESIGN Fifty-eight overweight and obese men and women [mean (+/-SD) body mass index (in kg/m(2)) = 31.8 +/- 4.5, age = 39.6 +/- 9.8 y, and maximal oxygen intake = 29.1 +/- 5.7 mL . kg(-1) . min(-1)] completed 12 wk of supervised exercise in the laboratory. The exercise sessions were designed to expend 2500 kcal/wk. Subjective appetite sensations and the satiating efficiency of a fixed breakfast were compared at baseline (week 0) and at week 12. An Electronic Appetite Rating System was used to measure subjective appetite sensations immediately before and after the fixed breakfast in the immediate postprandial period and across the whole day. The satiety quotient of the breakfast was determined by calculating the change in appetite scores relative to the breakfasts energy content. RESULTS Despite large variability, there was a significant reduction in mean body weight (3.2 +/- 3.6 kg), fat mass (3.2 +/- 2.2 kg), and waist circumference (5.0 +/- 3.2 cm) after 12 wk. The analysis showed that a reduction in body weight and body composition was accompanied by an increase in fasting hunger and in average hunger across the day (P < 0.0001). Paradoxically, the immediate and delayed satiety quotient of the breakfast also increased significantly (P < 0.05). CONCLUSIONS These data show that the effect of exercise on appetite regulation involves at least 2 processes: an increase in the overall (orexigenic) drive to eat and a concomitant increase in the satiating efficiency of a fixed meal.

Problems in identifying predictors and correlates of weight loss and maintenance: Implications for weight control therapies based on behaviour change

Weight management is a dynamic process, with a pre‐treatment phase, a treatment (including process) phase and post‐treatment maintenance, and where relapse is possible during both the treatment and maintenance.

Techniques for the study of energy balance in man

Energy balance can be estimated in tissues, body segments, individual subjects (the focus of the present article), groups of subjects and even societies. Changes in body composition in individual subjects can be translated into changes in the energy content of the body, but this method is limited by the precision of the techniques. The precision for measuring fat and fat-free mass can be as low as 0.5 kg when certain reference techniques are used (hydrodensitometry, air-displacement plethysmography, dual-energy X-ray absorptiometry), and approximately 0.7 kg for changes between two time points. Techniques associated with a measurement error of 0.7 kg for changes in fat and fat-free mass (approximately 18 MJ) are of little or no value for calculating energy balance over short periods of time, but they may be of some value over long periods of time (18 MJ over 1 year corresponds to an average daily energy balance of 70 kJ, which is < 1% of the normal dietary energy intake). Body composition measurements can also be useful in calculating changes in energy balance when the changes in body weight and composition are large, e.g. > 5-10 kg. The same principles can be applied to the assessment of energy balance in body segments using dual-energy X-ray absorptiometry. Energy balance can be obtained over periods as short as a few minutes, e.g. during measurements of BMR. The variability in BMR between individuals of similar age, weight and height and gender is about 7-9%, most of which is of biological origin rather than measurement error, which is about 2%. Measurement of total energy expenditure during starvation (no energy intake) can also be used to estimate energy balance in a whole-body calorimeter, in patients in intensive care units being artificially ventilated and by tracer techniques. The precision of these techniques varies from 1 to 10%. Establishing energy balance by measuring the discrepancy between energy intake and expenditure has to take into consideration the combined validity and reliability of both components. The measurement error for dietary intake may be as low as 2-3% in carefully controlled environments, in which subjects are provided only with certain food items and bomb calorimetry can be undertaken on duplicate samples of the diet. Reliable results can also be obtained in hospitalised patients receiving enteral tube feeding or parenteral nutrition as the only source of nutrition. Unreliability increases to an unknown extent in free-living subjects eating a mixed and varied diet; thus, improved methodology is needed for the study of energy balance.

Cognitive and weight-related correlates of flexible and rigid restrained eating behaviour.

OBJECTIVES Examine the association between components of restrained eating, cognitive performance and weight loss maintenance. METHODS 106 women, all members of a commercial slimming organisation for at least 6 months (mean±SD: 15.7±12.4 months), were studied who, having lost 10.1±9.7 kg of their initial weight, were hoping to sustain their weight loss during the 6 month study. Dietary restraint subcomponents flexible and rigid restraint, as well as preoccupying cognitions with food, body-shape and diet were assessed using questionnaires. Attentional bias to food and shape-related stimuli was measured using a modified Stroop test. Working memory performance was assessed using the N-back test. These factors, and participant weight, were measured twice at 6 month intervals. RESULTS Rigid restraint was associated with attentional bias to food and shape-related stimuli (r=0.43, p<0.001 resp. r=0.49, p<0.001) whereas flexible restraint correlated with impaired working memory (r=-0.25, p<0.05). In a multiple regression analyses, flexible restraint was associated with more weight lost and better weight loss maintenance, while rigid restraint was associated with less weight loss. CONCLUSIONS Rigid restraint correlates with a range of preoccupying cognitions and attentional bias to food and shape-related stimuli. Flexible restraint, despite the impaired working memory performance, predicts better long-term weight loss. Explicitly encouraging flexible restraint may be important in preventing and treating obesity.

Understanding the role of life events in weight loss and weight gain

This study explored the role of life events in triggering both weight loss and weight gain and assessed whether a number of variables differentiated between these two types of weight change. Members of a slimming club (n = 538) completed an online questionnaire concerning two events, which had caused either weight loss or weight gain. They then described the event and its impact in terms of a number of variables. The majority of participants could describe a time when a life event had resulted in both weight loss and weight gain including relationship problems, pregnancy, illness and death of someone close. Compared with the weight gain event, the weight loss event was perceived as more positive, less negative, more controllable and more predictable than the weight gain event. Further, in terms of sustaining conditions, the weight loss event was perceived as reducing the choice over food and the function of eating and as increasing the choice over exercise and the function of this behaviour. To conclude, life events are related to weight change and the direction of this change can be explained both by the perceived nature of the event and its impact upon choice and function of eating and exercise.

Experience and acceptability of diets of varying protein content and glycemic index in an obese cohort: results from the Diogenes trial

Background/Objectives:To investigate acceptability and tolerability of diets of different protein and glycemic index (GI) content aimed at weight maintenance following a phase of rapid weight loss, as part of a large pan-European dietary intervention trial.Subjects/Methods:The Diogenes study (www.diogenes-eu.org) consisted of an initial 8-week rapid weight-loss phase (800–1000 kcal/day), followed by a 6-month weight maintenance intervention with five different diets varying in protein and GI content. Measurement of a range of outcomes relating to experience of the Diogenes diets in terms of acceptability, experience and mood were recorded via end of day questionnaires throughout the study.Results:Weight change during the initial weight loss phase weakly, but positively correlated with acceptability of the programme (r range=−0.08 to 0.2, P⩽0.05, n=685 on four of five dimensions). Success at weight maintenance positively correlated with acceptance of the programme (r range=−0.21 to −0.34, P<0.001, n=540 for all five dimensions). The diets with higher protein content were more acceptable than the low protein (LP) diets, however, no differences between the high vs low GI diets were found concerning acceptability and tolerability.Conclusions:Results suggest that moderately high protein diets, compared with LP diets, are more acceptable diets for weight control in overweight individuals.

Effects of increasing increments of fat- and sugar-rich snacks in the diet on energy and macronutrient intake in lean and overweight men

Two studies have examined the effect on energy intake and macronutrient selection of increasing increments of mandatory high-fat or high-sugar snacks into the diet in men. The present study used a within-subject, repeated-measures design. In each experiment, six lean and six overweight, unrestrained men were each studied over three 7 d treatment periods, during which they were given mandatory snacks of the same energy density (550 kJ/100 g) comprising the following (in terms of percentage energy as fat-carbohydrate-protein): high-fat, 80:10:10; high-sugar, 10:80:10, of which 65 % was sugar, and 15 % starch. Subjects were given 0, 1.5 or 3.0 MJ/d snacks, in a randomised counterbalanced design, to be consumed mid-morning and mid-afternoon. Throughout each day, subjects had access ad libitum to fifteen high-protein, fifteen high-fat and fifteen high-carbohydrate foods, rotated on a 3 d menu. Mandatory high-fat snacks significantly elevated energy intake and fat intake, whereas high-sugar snacks elevated energy intake and carbohydrate intake (all P<0.02). Mandatory increases in sugar intake did not displace fat from the diet or vice versa. It was concluded that the ingestion of up to 3 MJ/d high-fat and high-sugar foods promoted weak compensation (18 % and 30 %, respectively) and therefore elevated daily energy intake by approximately 2.0-2.5 MJ.

Influence of Slimming World’s lifestyle programme on diet, activity behaviour and health of participants and their families

BACKGROUND Understanding the impact of commercial weight management programmes on behaviour change is an area that requires greater evidence. The present study investigated the impact of a commercial weight management organisations diet and activity programmes on the lifestyles of those accessing the services and their families. METHODS This survey was based on self-reports from a group of people involved in their own weight control. A questionnaire consisting of multiple choice and open-ended questions regarding diet, activity patterns and health was distributed in a commercial slimming organisations magazine and was available on the website for a 4 week period. Two thousand eight hundred and twelve respondents were analysed, including the organisations members (53%) and nonmembers (47%). RESULTS Those following the dietary programme reported significant changes towards healthier food choices in line with current guidelines (P < 0.01). Over 80% reported an improvement in their own health and over 26% reported an improvement in their partners or familys health (P < 0.01). Respondents reported increasing physical activity after being made aware of the organisations activity programme (P < 0.001). Members were more likely to have become more active than nonmembers (P = 0.011). The longer respondents had been members, the more likely they were to report an increased participation in physical activity (P = 0.02). Half of those reporting increased activity indicated that their partner or whole family had also increased their activity levels. CONCLUSIONS The commercial slimming organisations programme appeared to be having a beneficial impact on the diet and activity behaviours of those accessing the service. Group members were more likely to make positive behaviour changes and health improvements tended to increase with the duration of membership. The improvements observed with respect to both diet and activity levels also reached the wider family network.