R J Stubbs

The effect of graded levels of exercise on energy intake and balance in free-living women †

Aim: We assessed the effect of graded increases in exercised-induced energy expenditure (EE) on appetite, daily energy intake (EI), total daily EE and body weight in six lean women using a within-subject, repeated measures design.Method: Subjects were each studied three times during 7 day treatments, corresponding to no-exercise (control; Nex; 0 MJ/day), medium exercise level (Mex; ∼1.9 MJ/day) and high exercise level (Hex; ∼3.4 MJ/day), with 2 day maintenance beforehand. Subjects self-weighed ad libitum food intake. EE was assessed by continual heart rate monitoring. During waking hours subjects recorded hourly sensations of hunger and appetite.Results: EE amounted to 9.2, 11.0 and 12.1 MJ/day (F (2, 10)=5.67; P=0.023 (s.e.d.=0.87)) on the Nex, Mex and Hex treatments, respectively. The corresponding values for EI were 8.9, 9.2 and 10.0 MJ/day (F (2, 10)=4.80; P=0.035 (s.e.d.=0.36)). There were very weak treatment effects on hunger. Weight loss was significantly different from zero on the Mex and Hex treatments.Conclusion: Markedly increasing EE through exercise produced significant but partial compensations in EI (∼33% of EE due to exercise). Accurate adjustments of El to acute increases in EE are likely to take weeks rather than days.

The effect of covertly manipulating the energy density of mixed diets on ad libitum food intake in 'pseudo free-living' humans

OBJECTIVE: This study examined the effects of covert alterations in the energy density (ED) of mixed, medium fat (MF) diets on ad libitum food and energy intake (EI), subjective hunger and body weight in humans.DESIGN: Randomised cross-over design. Subjects were each studied three times (factorial design), during 14 d, throughout which they had ad libitum access to one of three covertly-manipulated MF diets.SUBJECTS: Six healthy men, mean age (s.e.m.)=30.0 y (12.76 y), mean weight=71.67 kg (19.80 kg); mean height=1.79 m (0.22 m), body mass index (BMI)=22.36 (2.60) kg/m2, were studied. The fat, carbohydrate (CHO) and protein in each diet (as a proportion of the total energy) and energy density (ED) were, low-ED (LED), 38:49:13%; 373 kJ/100 g; medium-ED (MED), 40:47:13%; 549 kJ/100 g; high-ED (HED), 39:48:13%; 737 kJ/100 g. Subjects could alter the amount but not the composition of foods eaten. They were resident in (but not confined to) a metabolic suite throughout the study.RESULTS: Solid food intake decreased as ED increased, giving mean values of 2.84, 2.51 and 2.31 kg/d, respectively. This was insufficient to defend energy balance, since energy intake increased with increasing ED (F (2,10) 16.08; P<0.001) giving mean intakes of 10.12, 12.80 and 16.17 MJ/d, respectively. Rated pleasantness of food (measured on visual analogue scales) was not significantly different between diets nor was subjective hunger different between the LED, MED and HED diets, respectively. Diet significantly affected body weight (F (2,10)=4.62; P=0.038), producing changes of −1.20, +0.02 and +0.95 kg, respectively, by day 14.CONCLUSION: Dietary ED can influence EI and body weight, since changes in amount eaten alone are insufficient to defend energy balance, when subjects feed on unfamiliar diets and diet selection is precluded. Comparison with our previous studies suggest that there was compensation in solid food intake when ED was altered using mixed diets (as in this study) compared to previous studies which primarily used fat or CHO to alter dietary ED.

Comparison of the traditional paper visual analogue scale questionnaire with an Apple Newton electronic appetite rating system (EARS) in free living subjects feeding ad libitum

Objective: Assessing the value of a newly developed electronic visual analogue scale questionnaire (Apple Newton Message Pad) with the traditional paper method for appetite rating.Design: In a random, crossover design, subjects completed both electronic and paper questionnaires to compare results obtained by the two methods; individual methods were completed consecutively to assess test-retest reliability; preference was established using a questionnaire.Setting/Subjects: Healthy, free-living adults were studied for comparison of methods (n=12), test-retest reliability (n=8) and preference (n=13).Intervention: Visual analogue scales were completed each waking hour to assess appetite. Preference was assessed after both methods were completed.Results: There was no significant difference in the hourly results obtained by the paper and electronic methods for ‘desire to eat’, ‘how much can you eat now’, ‘urge to eat’ and ‘preoccupation with thoughts of food’. Small differences in ‘hunger’ and ‘fullness’ ratings were noted (∼5% mean difference between methods, P<0.05), but patterns of change and sensitivity for these and all other parameters remained similar for both methods across the visual analogue scale. Test-retest reliability demonstrated was similar for both methods. Seven (54%) subjects preferred to use the paper questionnaire, five (38%) the electronic method and one (8%) had no preference.Conclusions: The electronic Apple Newton questionnaire is as sensitive and reliable as the paper method, has the advantage that it automatically records the time of data acquisition and data collection and processing are more efficient for the researcher. The two methods should not be used interchangeably.Sponsorship: Medical Research Council.

Beneficial effects of exercise: shifting the focus from body weight to other markers of health

Background: Exercise is widely promoted as a method of weight management, while the other health benefits are often ignored. The purpose of this study was to examine whether exercise-induced improvements in health are influenced by changes in body weight. Methods: Fifty-eight sedentary overweight/obese men and women (BMI 31.8 (SD 4.5) kg/m2) participated in a 12-week supervised aerobic exercise intervention (70% heart rate max, five times a week, 500 kcal per session). Body composition, anthropometric parameters, aerobic capacity, blood pressure and acute psychological response to exercise were measured at weeks 0 and 12. Results: The mean reduction in body weight was −3.3 (3.63) kg (p<0.01). However, 26 of the 58 participants failed to attain the predicted weight loss estimated from individuals’ exercise-induced energy expenditure. Their mean weight loss was only −0.9 (1.8) kg (p<0.01). Despite attaining a lower-than-predicted weight reduction, these individuals experienced significant increases in aerobic capacity (6.3 (6.0) ml/kg/min; p<0.01), and a decreased systolic (−6.00 (11.5) mm Hg; p<0.05) and diastolic blood pressure (−3.9 (5.8) mm Hg; p<0.01), waist circumference (−3.7 (2.7) cm; p<0.01) and resting heart rate (−4.8 (8.9) bpm, p<0.001). In addition, these individuals experienced an acute exercise-induced increase in positive mood. Conclusions: These data demonstrate that significant and meaningful health benefits can be achieved even in the presence of lower-than-expected exercise-induced weight loss. A less successful reduction in body weight does not undermine the beneficial effects of aerobic exercise. From a public health perspective, exercise should be encouraged and the emphasis on weight loss reduced.

Covert manipulation of energy density of high carbohydrate diets in 'pseudo free-living' humans

OBJECTIVE: This study examined the effects of varying the energy density (ED) of high carbohydrate (HC) diets on food and energy intake (EI), subjective hunger and body weight in humans.DESIGN: Randomised cross-over design. Subjects were each studied twice during 14 d, throughout which they had ad libitumaccess to one of two covertly-manipulated diets.SUBJECTS AND METHODS: Six healthy men (mean age (s.d.)=32.17 y s.d. (5.26 y), mean weight=69.74 kg s.d. (2.75 kg), mean height=1.76  m s.d. (0.05 m), body mass index (BMI)=22.57 (2.2) kg/m2) were studied. The fat, carbohydrate (CHO) and protein content (as % energy) and ED of each diet were 21∶66∶13% and 357 kJ/100 g, (low-energy density (LED)) or 22∶66∶12% and 629 kJ/100 g (high-energy density (HED)). A medium fat diet was provided at maintenance (1.6×BMR, MF for 2 d) before each ad libitumperiod. Subjects could alter the amount, but not the composition of foods eaten.RESULTS: Mean EI was 8.67 and 14.82 MJ/d on the LED and HED diets, respectively. Subjects felt significantly more hungry on the LED diet, than on the HED diet (F1,16038.28; P<0.001) and found the diets to be similarly pleasant (72.72 mm vs 71.54 mm (F1,3920.31; P=0.579)). Mean body weight decreased on the LED diet at a rate of 0.1 kg/d and increased at 0.06 kg/d on the HED diet (F1,13186.60; P<0.001), giving total weight changes of −1.41 kg and +0.84 kg, respectively, both of which were significantly different from zero (P<0.01).CONCLUSION: Excess EI is possible on HC, HED diets, at least under conditions where diet selection is precluded. Comparison of these results with previous studies, which altered ED using fat, suggests that CHO may be a better cue for hunger than fat.

Exercise alone is not enough: weight loss also needs a healthy (Mediterranean) diet?

OBJECTIVE In the majority of exercise intervention studies, the aggregate reported weight loss is often small. The efficacy of exercise as a weight loss tool remains in question. The aim of the present study was to investigate the variability in appetite and body weight when participants engaged in a supervised and monitored exercise programme. DESIGN Fifty-eight obese men and women (BMI = 31.8 +/- 4.5 kg/m2) were prescribed exercise to expend approximately 2092 kJ (500 kcal) per session, five times a week at an intensity of 70 % maximum heart rate for 12 weeks under supervised conditions in the research unit. Body weight and composition, total daily energy intake and various health markers were measured at weeks 0, 4, 8 and 12. RESULTS Mean reduction in body weight (3.2 +/- 1.98 kg) was significant (P < 0.001); however, there was large individual variability (-14.7 to +2.7 kg). This large variability could be largely attributed to the differences in energy intake over the 12-week intervention. Those participants who failed to lose meaningful weight increased their food intake and reduced intake of fruits and vegetables. CONCLUSION These data have demonstrated that even when exercise energy expenditure is high, a healthy diet is still required for weight loss to occur in many people.

Effect of an acute fast on energy compensation and feeding behaviour in lean men and women.

AIM: Humans appear to defend against energy deficit to a greater extent than energy surplus. Severe dietary energy restriction resulting in 5–30% weight loss often leads to hyperphagia and weight regain in lean subjects. However, the period of time over which fasting is often endured in Western society are far shorter, ∼1–2 days. This study examined how a 36 h fast effected the subsequent days energy and nutrient intake in a group of 24 healthy, lean men and women.METHOD: Subjects underwent two 2 day treatments, termed ‘fast’ and ‘maintenance’. During the ‘fast’ treatment, subjects were fed a maintenance diet on the day prior to the fast (day −1) to prevent overeating. They then consumed non-energy drinks only, from 20:00 h on day −1 to 08:00 h on day 2 (ad libitum feeding day), thus fasting for 36 h. On the ‘maintenance’ protocol, subjects received a maintenance diet throughout day 1. Throughout day 2 they had ad libitum access to a range of familiar foods, which were the same for both treatments. Body weight, blood glucose and respiratory quotient were used as compliance checks. Hunger was monitored on days −1, 1 and 2 for the fast treatment only.RESULTS: On day 2, average energy intake was 10.2 vs 12.2 MJ/day (s.e.d. 1.0) on the post-maintenance and post-fast periods, respectively (P=0.049). Subjects altered feeding behaviour, in response to the fast, only at breakfast time, selecting a higher-fat meal (P<0.005). Compared to day −1, motivation to eat was elevated during the fast (P<0.05). This continued until breakfast was consumed during the re-feeding period (day 2), when values then returned to baseline.CONCLUSION: These data suggest that a 36 h fast, which generated a negative energy balance of ∼12 MJ, did not induce a powerful, unconditioned stimulus to compensate on the subsequent day.

Use of the cellular model of body composition to describe changes in body water compartments after total fasting, very low calorie diet and low calorie diet in obese men.

Introduction:The cellular model of body composition divides the body in body cell mass (BCM), extracellular solids and extracellular fluids. This model has been infrequently applied for the evaluation of weight loss (WL) programmes.Objectives:(1) To assess changes in body compartments in obese men undergoing fasting, very low calorie diet (VLCD) and low calorie diet (LCD); (2) to evaluate two cellular models for the determination of changes in BCM, fat mass (FM) and body fluids.Materials and methods:Three groups of six, obese men participated in a total fast (F) for 6 days, a VLCD (2.5 MJ per day) for 3 weeks or an LCD (5.2 MJ per day) for 6 weeks. Body composition was measured at baseline and after small (∼5%) and moderate (∼10%) WL. FM was measured using a four-compartment model. Total body water (TBW) and extracellular water (ECW) were, respectively, measured by deuterium and sodium bromide dilution and intracellular water (ICW) calculated by difference. Two cellular models were used to measure BCM, FM and body fluids distribution.Results:After about 5%WL changes in TBW were F=−3.2±1.2 kg (P<0.01), VLCD=−1.2±0.6 kg (P<0.01), LCD=−0.3±0.9 kg(n.s.). The contribution of TBW to total body mass loss was indirectly associated with FM loss. ECW increased during fasting (+1.5±3.1 kg, n.s.), decreased during the VLCD (−2.0±1.5 kg, P<0.05) and remained unchanged at the end of the LCD (−0.3±1.6 kg, n.s.). ICW significantly decreased during fasting (−4.7±3.9 kg, P<0.05) but did not change in the LCD and VLCD groups. The loss of BCM was more significant in the fasting group and it was directly associated with changes in ICW.Conclusions:After a 6-day period of fasting we observed more ICW losses and less fat mobilization compared with VLCD and LCD. The cellular model of body composition is suitable for the characterization of changes in body fluids distribution during WL.

Low-energy reporting and duration of recording period.

Three-day, rather than 7-day, food records are frequently used because mis-reporting of food intake is believed to increase with recording period. Data from the National Diet and Nutrition Survey of adults were used to explore trends in reported energy intake (REI) with day of recording and to compare average REIs from Thursday to Saturday and from Sunday to Tuesday to the complete 7-day record. Although REIs decreased from days 2 to 7, this was by a quantitatively insignificant 49 kJ per day (P=0.026) and well within the measurement error of recorded food intakes. Furthermore, REIs were lowest on the first recording day. The 3- and 7-day averages were similar (mean difference 0.039 (s.d.±1.0) MJ (NS), range −3.3 to +4.2 MJ). However, the difference was greater for those reporting higher than average energy intakes because of higher REIs on weekend days. Food intake reporting periods of longer than 3 days and ideally 7 days are preferable.

Comparing different measures of energy expenditure in human subjects resident in a metabolic facility.

Objective:To compare energy expenditure (EE) measured by doubly labeled water (DLW) with other measures, both physical and based on subjective questionnaires.Design:A comparison of methods in a stratified sample of adult volunteers.Setting:The feeding behaviour suite (FBS) at the Rowett Research Institute, Aberdeen.Subjects:A total of 59 subjects, stratified for age, sex and body mass index (BMI).Interventions:EE was assessed by DLW (validated using measurements of energy balance), heart rate monitor (HRM), activity monitor (Caltrac), 24-h physical activity diary (PAD) and 7-day physical activity recall. Energy intake was assessed using covert (investigator-weighed) food intake (EI). Data were collected over a 12-day period of residence in the Rowetts FBS.Results:No methods correlated highly with physical activity assessed by DLW. Physical methods correlated more closely than did subjective recording. All methods (except EI) significantly underestimated EE, estimated by DLW. There were no significant differences in association between methods and sex, age, BMI or fat-free mass.Conclusion:EE is difficult to measure precisely or accurately with current approaches but physical methods are slightly better than subjective accounts.