What is the best diet to recommend when treating obesity

Objective. The objective of this narrative review is to examine empirical data on the optimal type of diet for individuals with established obesity who are being treated by an exercise-centred weight reduction programme. The first section of the review examines the influence of eating patterns and differences in the sugar and salt content of foods upon weight maintenance. A second section considers the choice between high-carbohydrate, high-fat and high-protein diets, and a third section explores issues of water and fibre intake, along with other possible dietary options for those attempting to reduce their weight. Methods. Information obtained from Ovid/Medline, PubMed and Google Scholar through to August 2019 has been supplemented by a search of the author's extensive personal files. Results. A person's immediate energy intake increases with the portion-size of foods that are offered, apparently without change of satiety, and the individual seems to make an incomplete subsequent adjustment for any resultant excess of food consumption. Epidemiological studies suggest that sweetness has some effect in increasing food intake, with heavier body weights being found in those who consume large amounts of sweetened foods or drinks, but in short-term experiments subjects compensate at least partially for the energy content of sweetened drinks and foods by reducing their food intake at a subsequent meal. The salt content of food also has some effect on appetite; more tests are needed looking at the salt content of fast foods, but in normal home cooking the appetite-stimulating effect of salt seems less than was once thought. In cross-sectional analyses, the practice of skipping breakfast and the frequent consumption of "fast" foods are often associated with difficulties of weight control, but this is probably because those with poor dietary habits have a limited interest in adopting any aspect of a healthy lifestyle. Fast foods have had little apparent influence on obesity in randomized controlled trials. Likewise, the practice of frequent snacking shows little relationship to obesity once allowance has been made for associated television watching and a low level of habitual physical activity. Cross-sectional comparisons suggest that the risk of obesity is lower in those who take more frequent meals per day, but again this could be an artifact of reverse causation, with obese individuals reducing the frequency of their meals in an attempt to lose weight. Conclusions. Public health measures to reduce the portion size and/or energy density of foods seem warranted. A small tax seems an effective method of reducing the consumption of sweetened drinks, but large changes in the salt content of food seem to have little impact upon the palatability of food. Many variations of eating habits have shown cross-sectional associations with problems of weight control, but it remains difficult to disentangle the influence of co-variates such as habitual physical activity, socio-economic status, and overall interest in a healthy lifestyle. Nevertheless, smaller portion sizes, a reduction of sugar and salt intake, and frequent regular meals seem good nutritional recommendations for those who are seeking to reduce their body weight.