OBJECTIVE: To investigate the degree of bias in under-reporting of food intake in obese and non-obese subjects, hypothesising that under-reporting may be selective for either macronutrient content (carbohydrate (CHO), fat, protein, alcohol), speci®c food types or eating occasions (meals, snacks). DESIGN: Thirty-three women (18 obese, 15 non-obese) were recruited to a long-stay metabolic facility for 24 h. Ad libitum food intake was covertly measured throughout the study and a reported food intake completed at the end of 24 h. RESULTS: Reported total daily energy intake was signi®cantly lower than measured intake. Whilst meals were accurately reported, energy from snack foods eaten between meals was signi®cantly under-reported. (P`0.001) Reported total carbohydrate and added sugar intakes were signi®cantly lower than measured, whilst reported protein and fat intakes were not signi®cantly different from measured. Reported alcohol intake was also considerably lower than measured, but high variability prevented signi®cance. CONCLUSIONS: In both obese and non-obese women the major cause of under-reporting, as assessed by covert study design in subjects restricted within a metabolic facility, is the failure to report between-meal snack foods. There is some evidence for increased under-reporting in high CHO, but no evidence of a bias in under-reporting towards high fat or high protein foods.

OBJECTIVE: To investigate the long-term effects of changes in dietary carbohydrateafat ratio and simple vs complex carbohydrates. DESIGN: Randomized controlled multicentre trial (CARMEN), in which subjects were allocated for 6 months either to a seasonal control group (no intervention) or to one of three experimental groups: a control diet group (dietary intervention typical of the average national intake); a low-fat high simple carbohydrate group; or a low-fat high complex carbohydrate group. SUBJECTS: Three hundred and ninety eight moderately obese adults. MEASUREMENTS: The change in body weight was the primary outcome; changes in body composition and blood lipids were secondary outcomes. RESULTS: Body weight loss in the low-fat high simple carbohydrate and low-fat high complex carbohydrate groups was 0.9 kg (P`0.05) and 1.8 kg (P`0.001), while the control diet and seasonal control groups gained weight (0.8 and 0.1 kg, NS). Fat mass changed by 7 1.3 kg (P`0.01), 7 1.8 kg (P`0.001) and 0.6 kg (NS) in the low-fat high simple carbohydrate, low-fat high complex carbohydrate and control diet groups, respectively. Changes in blood lipids did not differ signi®cantly between the dietary treatment groups. CONCLUSION: Our ®ndings suggest that reduction of fat intake results in a modest but signi®cant reduction in body weight and body fatness. The concomitant increase in either simple or complex carbohydrates did not indicate signi®cant differences in weight change. No adverse effects on blood lipids were observed. These ®ndings underline the importance of this dietary change and its potential impact on the public health implications of obesity.

It is frequently claimed that weight cycling, or "yo-yo" dieting, causes an inappropriate and permanent loss of lean body mass (LBM). Data are presented from a rural African population that undergoes profound weight cycling caused by an annual hungry season. No detrimental effect on LBM was observed. Data are also presented from an 18-wk prospective study of moderately obese British women who underwent three cycles of VLCD-induced weight loss and subsequent relapse. The proportion of weight lost as LBM was no greater than predicted. A review of the published results from experimental weight cycling in small animals also shows a high level of consensus that cycling does not significantly alter body composition. We conclude that, although weight cycling may affect growth of young animals, metabolic efficiency, and health, these effects are not mediated through permanent alterations in body composition.

Objective: To investigate the effect of moderate changes in dietary fatty acid profile on postprandial risk factors for cardiovascular disease (CVD). Design: Double-blind, randomised, crossover, intervention trial. Setting: University of Auckland Human Nutrition Unit, New Zealand. Subjects: A total of 18 lean healthy men. Intervention: A dairy butter fat modified to reduce the saturated:unsaturated fatty acid ratio and a conventional high saturated butter fat were given on two separate occasions as a high-fat test meal (5974 g fat; 71 en% fat) at breakfast. A fat exclusion lunch, dinner and snacks were also given. Blood samples were collected at 0 (baseline), 1, 3, 6, 10 and 24 h. Results: Maximum peak in total triacylglycerol (TAG) occurred 3 h postprandially and was highest on modified treatment (diet, Po0.05) due predominantly to increased TAG within the chylomicron-rich fraction. Transient peaks in total-, LDL-and HDLcholesterol occurred postprandially, but did not differ between dietary treatments (P40.05). There were no differential effects of diet on postprandial free fatty acids, apo A, apo B, glucose, insulin, amylin or haemostatic clotting factors (P40.05). Conclusions: In a group of healthy young men, replacement of 16% of total saturated fatty acids by mono-and polyunsaturated fats within a dairy lipid did not induce postprandial changes in CVD risk that may be considered beneficial for health.