Dietary Factors in Childhood Obesity

Obesity is a disease that combines the influence of a genetic predisposition with an obesogenic environment. Our purpose is to review the role of dietary factors in the developement and the maintenance of obesity in children, and to point out the alterations of energy balance induced by energy restriction. There is considerable evidence that a genetic susceptibility to fat gain is necessary to override the regulatory systems of energy intake. Therefore, only children highly sensitive to the abundant palatable food in the environment can develop obesity. The current way of life in industrialized countries, but also the socioeconomic development of urban areas in transitional nations, provide such a condition. Despite conflicting results in the literature, obese children must have increased energy intake in order to match their enhanced energy expenditure. Extra-prandial intake and higher proportion of energy intake during the second part of the day contribute to a positive energy balance, although these food intake patterns are not specific to obese children. Similarly, whatever the relative proportion of fat or carbohydrate intake, an excess in total energy intake is an absolute requisite to lead to weight gain. The discrepancies about the role of food portion size and energy density, sugar-sweetened drinks, added sugars and high-glycemic index meals in the development and the maintenance of childhood obesity are discussed. The compensatory mechanisms which offset the effects of diet, explaining the poor therapeutic results of the treatment, will also be dealt with. Further research focused on the genetic and metabolic control of food intake should be developed to curb the increasing prevalence of childhood obesity.