The rapid global rise of obesity incurs a heavy personal and healthcare burden due to obesity-associated morbidities and shortening of life. The purpose of this review is to provide evidence-based strategies for prevention, reversal, and mitigation of obesity and its sequelae. To that end, this review highlights the features of human physiology that favor fat accretion and interfere with fat loss. Strategies for prevention of obesity include understanding the basis for the strong motivating properties of palatable food, for human inability to consciously detect calories eaten or calories expended through exercise, for metabolic and hormonal adaptations to negative energy balance that drive weight regain, and for evolutionary natural selection which likely led to high human capacity for fat storage. Reversal of obesity is difficult primarily due to metabolic, hormonal, and behavioral reactions to body fat loss. Reduced resting metabolic rate presents a physiological challenge whether the weight loss is achieved through dietary restriction or energy expenditure of exercise. Increased insulin sensitivity after body fat loss drives resynthesis of storage substrates including triglycerides in the adipose tissue, muscle glycogen, and proteins, thus contributing to weight regain. Reduced basal plasma leptin concentration elicits a strong hunger drive. Mitigation of obesity-associated morbidities involves adding exercise energy expenditure to deliberate control of the quantity of food eaten, reducing postprandial hyperinsulinemia by lowering the carbohydrate load of the diet, and exercising after, rather than before, the meals to facilitate improved glucose tolerance.
Physical Exercise, Energy Expenditure and Weight Loss: An Assumption not Always Observed in Practice