The effect of macronutrients on body composition and appetite regulation
Creators: name: Pettitt, Claire Louise
Publisher: name: Imperial College London
Year: 2020

description: Current dietary interventions in the treatment of obesity are struggling to prevent its increasing global prevalence and detrimental side-effects, including non-alcoholic fatty liver disease (NAFLD). Many studies addressing the macronutrient content of the human diet have shown that manipulation of the macronutrient makeup of the diet may have beneficial effects on weight loss, appetite regulation, body composition and metabolic health. However, obesity and nutrition research are flawed by the limitations of current dietary recording methodologies, as there is an inverse relationship between accuracy of reporting of energy intake by all current nutritional methodologies and body weight. This work aimed to determine the effects of specific individual nutrients (a high-protein, hypo-caloric diet, and long chain n3-polyunsaturated fatty acids (n3-PUFA) supplementation with a hypocaloric diet) on weight, adiposity and appetite in overweight participants. In addition to this a pilot study explored the use of a novel lightweight wearable micro-camera in improving the accuracy of dietary intake assessment. Anthropometric measurements were taken using weight, body mass index (BMI), waist circumference (WC), hip circumference (HC), bioelectrical impedance (BIA), and the gold standard for measuring body composition, magnetic resonance imaging (MRI). Energy intake and appetite was measuring using a 3- or 7-day food diary, an ad-libitum meal, visual analogue scale and, for the n3-PUFA study, fMRI was also employed to assess changes in food reward through measuring changes in blood oxygen level dependent (BOLD) signal in response to food images. The results suggest that any changes in body composition, biochemistry and appetite induced by a 12-week hypocaloric diet appear to be independent of protein content (body weight change of -4.06±0.85kg body weight with normal protein vs -4.42±0.85kg with high protein diet), whilst n3 PUFA supplementation during a calorie restricted diet may improve weight loss (-2.53kg±0.59kg, p&lt;0.0001 weight loss seen with n3 PUFA vs -0.05±0.64kg, p=0.419 seen in the placebo group), through improved compliance to the calorie-restricted diet (energy intake compared to baseline was 298 ± 93kcals lower in the placebo group and 524 ± 69kcals lower in the PUFA group). The mechanism behind this improved compliance and enhanced weight loss has not been elucidated, however it seems it is not mediated by changes in appetite or via reward pathways. The microcamera does improve the accuracy of dietary assessment and provides valuable information on macronutrient intake and eating rate. However, there is a need to develop this recording technique to increase its usability and remove user and assessor bias. Our study adds to the research suggesting that n3 PUFA supplementation has a role to play in modifying, particularly reducing, body weight and body composition, and although we found no significant effects with the high protein diet, further work should seek to understand the optimum and minimum effective dose and duration of treatment with n3 PUFA and/or high protein diets.