What is the best diet to recommend when treating obesity by an increase of habitual physical activity?

3. The roles of water, fibre intake, and other possibly helpful nutritional options.

Abstract

Objective. The objective of this three-part narrative review has been to examine empirical data on the optimal type of diet to recommend when individuals with established obesity are being treated by a programme of moderate exercise coupled with some reduction of daily energy intake. The final section of this review considers the potentially beneficial influence of an increased water and fibre intake, along with other possibly helpful nutritional options. Methods. Information obtained from Ovid/Medline, PubMed and Google Scholar through to September 2019 as been supplemented by a search of the author's extensive personal files. Results. Drinking additional water or adding water to a food product may reduce immediate hunger and thus the overall intake of food, replace the previous consumption of sugar-containing drinks, and possibly increase thermogenesis by an osmotic mechanism. Longitudinal studies give tentative evidence that increased water ingestion has some beneficial effect upon body mass, greater in the obese than in individuals of normal weight. A high fibre content also increases satiety, but randomized controlled trials show that such a diet has little advantage in terms of eventual weight loss. Other potentially beneficial options include an increased consumption of nuts, yogurt and calcium. In cross-sectional analyses, nut consumption is inversely associated with body weight, but short-term experimental increases of nut consumption have had little influence upon body mass. Yogurt has also been suggested as helping the process of weight loss, but again there are as yet few randomized controlled trials supporting such an idea. Cross-sectional and cohort studies, almost without exception, have shown better weight regulation in groups receiving calcium supplements or an increased intake of dairy products, but in contrast there is either no effect or at most a quite small benefit to be seen in randomized trials. Conclusions. Available randomized studies suggest that the fat loss achieved by a combination of moderate physical exercise and some restriction of energy intake is similar for those following a variety of diets and nutritional tactics. Challenges to health professionals are to maintain a blood glucose level that avoids a deterioration of mood and a reduction of voluntary exercise, to maintain lean tissue mass and thus resting metabolic rate, and to sustain satiety and thus the enthusiasm needed to persist with the prescribed regimen.