Compared with nibbling, neither gorging nor a morning fast affect short-term energy balance in obese patients in a chamber calorimeter.

OBJECTIVE: To test if a diet of 4.2 MJ/24 h as six isocaloric meals would result in a lower subsequent energy intake, or greater energy output than (a) 4.2 MJ/24 h as two isocaloric meals or (b) a morning fast followed by free access to food. DESIGN: Subjects were confined to the Metabolic Unit from 19:00 h on day 1 to 09:30 h on day 6. Each day they had a fixed diet providing 4.2 MJ with three pairs of meal patterns which were offered in random sequence. They were: six meals vs two meals without access to additional foods (6vs2), or six meals vs 2 meals with access to additional food (6+vs2+), or six meals vs four meals (6+vsAMFAST). In the AMFAST condition the first two meals of the day were omitted to reduce daily intake to 2.8 MJ and to create a morning fast, but additional food was accessible thereafter. Patients were confined in the chamber calorimeter from 19:00 h on day 2 until 09:00 h on day 4, and then from 19:00 h on day 4 to 09:00 h on day 6. The order in which each meal pattern was offered was balanced over time. MEASUREMENTS: Energy expenditure (chamber calorimetry), spontaneous activity (video) and energy intake (where additional foods were available) during the final 24 h of each dietary component. SUBJECTS: Ten (6vs2), eight (6+vs2+) and eight (6+vsAMFAST) women were recruited who had a BMI of greater than 25 kg/m2. RESULTS: From experiment 6vs2 the difference between energy expenditure with six meals (10.00 MJ) and two meals (9.96 MJ) was not significant (P=0.88). Energy expenditure between 23:00 h and 08:00 h ('night') was, however, significantly higher (P=0.02) with two meals (9.12 MJ/24 h) compared with six meals (8.34 MJ/24 h). The pattern of spontaneous physical activity did not differ significantly between these two meal patterns (P>0.05). Total energy intake was affected by neither meal frequency in experiment 6+vs2+ (10.75 MJ with six, 11.08 MJ with two; P=0.58) nor a morning fast in experiment 6+vsAMFAST (8.55 MJ/24 h with six, 7.60 MJ with AMFAST; P=0.40). The total diet of subjects who had a morning fast tended to have a lower percentage of total energy from carbohydrate (40%) than when they had six meals per 24 h (49%) (P=0.05). Subsequent energy balance was affected by neither meal frequency (6vs2; P=0.88, 6+vs2+; P=0.50) nor a morning fast (P=0.18). CONCLUSIONS: In the short term, meal frequency and a period of fasting have no major impact on energy intake or expenditure but energy expenditure is delayed with a lower meal frequency compared with a higher meal frequency. This might be attributed to the thermogenic effect of food continuing into the night when a later, larger meal is given. A morning fast resulted in a diet which tended to have a lower percentage of energy from carbohydrate than with no fast.

Randomised controlled trial of novel, simple, and well supervised weight reducing diets in outpatients.

OBJECTIVES: To investigate the contribution of novelty and simplicity to compliance with a low energy diet among obese outpatients. DESIGN: Three arm randomised trial for 16 weeks. SETTING: NHS hospital obesity clinic. SUBJECTS: 45 patients aged over 17 years with a body mass index >27 who were not diabetic, pregnant, or lactating. INTERVENTIONS: Conventional 3.4 MJ diet (control), isoenergetic novel diet of milk only, or milk plus one designated food daily. Follow up visit every 4 weeks. MAIN OUTCOME MEASURE: Weight loss. RESULTS: Mean weight loss (kg) after 16 weeks on control, milk only, and milk plus diets was 1.7 (95% confidence interval 0.3 to 3.7), 9.4 (5.9 to 12.9), and 7.0 (2.7 to 11.3) respectively. Weight loss on the novel diets was significantly greater than on the control diet. CONCLUSIONS: Dietary treatment can achieve as much weight loss in obese outpatients over 16 weeks as has been reported for the most successful drug treatment, but compliance with the prescribed diet is poor unless the diet is novel and simple.

Four years' experience of an undergraduate medical nutrition course.

In 1992 the medical colleges of The Royal London and St Bartholomew's hospitals launched a new curriculum in which basic medical sciences were to be integrated with early exposure to clinical medicine in the first phase. The curriculum was to be modular and integrative, combining clinical and medical-science-based teaching of body systems, rather than the traditional teaching by departmental discipline. We describe the inception, content and evaluation of a 7-day course on nutrition which was developed as part of this curriculum. It was rated highly by the students, whose feedback led to important modifications. The programme works well in practice, and could provide a useful guide for other schools about to set up nutrition courses for medical students.

Does moderate aerobic activity have a stimulatory effect on 24 h resting energy expenditure: a direct calorimeter study.

This study was designed to establish whether moderate aerobic exercise (2 h at 30-35% VO2 max) in lean non-athletic male adults had a prolonged stimulatory effect on energy expenditure while at rest. Four weight maintaining male adults had their 24 h energy expenditure measured by direct calorimetry on four separate occasions. During the 24 h in the calorimeter each subject received a diet which in total supplied 35 kcal (146 kJ) per kg body weight. All studies in an individual were completed within four to six weeks during which time body weight remained stable. On two of these 24 h periods, individuals rested throughout while on the other two, they also performed the prescribed exercise. This consisted of cycling for two 1 h sessions; the first while they were fasting while the second period was approximately 45 min after consuming a 800 kcal (3.4 MJ) meal. Total 24 h energy expenditure was greater on exercise (8.3 +/- 1.8 MJ/day) than non-exercising days (6.3 +/- 1.4 MJ/day, P < 0.001) In contrast when the acute effects of the cycling where removed 24 h resting energy expenditure on the exercise day (6.8 +/- 1.7 MJ/day) was not significantly different from that of rest days (95% confidence intervals of the difference ranged from -0.36 to 1.27 MJ/day). This study did not demonstrate a prolonged stimulatory influence on non-exercising resting energy expenditure following physical activity likely to be achieved by non-athletes. These data provide no evidence that such exercise is associated with a greater energy deficit than that due to the activity itself.

Meta-analysis: effect of exercise, with or without dieting, on the body composition of overweight subjects.

OBJECTIVE: To determine if physical training conserves fat-free mass (FFM) in overweight men or women during weight loss. DESIGN: Journals published between 1966 and 1993 were searched by MEDLINE and by handsearch to obtain all reports on human subjects in which the effect of exercise on body composition was studied in at least two concurrent treatment groups, of which at least one group did, and one group did not, undergo an exercise programme designed to promote fat loss. The relation between loss of weight, and loss of FFM, was examined by linear regression analysis among exercising and non-exercising groups of men or women. SUBJECTS: Twenty-eight publications reported results on 226 sedentary men in 13 groups, 233 exercising men in 14 groups, 199 sedentary women in 23 groups, and 258 exercising women in 28 groups. RESULTS: Aerobic exercise without dietary restriction among men caused a weight loss of 3 kg in 30 weeks compared with sedentary controls, and 1.4 kg in 12 weeks among women, but there was little effect on FFM. Resistance exercise had little effect on weight loss, but increased FFM by about 2 kg in men and 1 kg in women. Regression analysis shows that for a weight loss of 10 kg by diet alone the expected loss of FFM is 2.9 kg in men and 2.2 kg in women. When similar weight loss is achieved by exercise combined with dietary restriction the expected loss of FFM is reduced to 1.7 kg in men, and women. It is probable that the FFM conserved by exercise during weight loss contains more water and potassium than average FFM. The subjects studied were not severely obese. CONCLUSIONS: Aerobic exercise causes a modest loss in weight without dieting. Exercise provides some conservation of FFM during weight loss by dieting, probably in part by maintaining glycogen and water.

Comparison of estimates of fat-free mass in normal and obese women from measurements of body potassium, body water and body density.

The relation between the estimates of fat-free mass (FFM) obtained from measurements of density, total body potassium and water was investigated in 104 women with Quetelet's Index between 19.9 and 49.7 kg/m2, body weight between 42.3 and 133.5 kg. The mean difference between the estimates based on water and potassium, previously reported as 2.2 kg or 4.4 per cent, was found to be independent of Quetelet's Index. The mean difference (s.e.m.) between the estimates of FFM based on density, compared with the average values from water and potassium, was found to be +7.0 (1.0), +6.3 (0.7) and +7.4 (1.1) kg in the ranges of Quetelet's Index 19.9-30.0, 30.1-40.0, and 40.1-49.7, respectively. The relative independence on Quetelet's Index of the difference between the estimates based on density compared with (water + potassium) is consistent with the idea that tissues of a higher density (ie, skin and bone) make up a larger proportion of the fat-free body weight in thin subjects than in fat ones.