Is fat intake related to obesity? What is the evidence from the epidemiological point of view?

Heiner Boeing, Nuthetal

Epidemiological studies on fat intake concentrate on the primary prevention of obesity, i.e. on how to prevent obesity. These studies – preferentially a prospective follow-up of populations of normal weight – aim at determining those factors which predict weight gain. Studies on how to reduce body weight by a change in diet which are frequently performed as double blind randomized intervention studies, serve as secondary or tertiary prevention of obesity.

A positive energy balance increases body weight up to the moment at which a balance is restored by the higher energy expenditure following weight gain. It has been shown, on the one hand, that energy supplied by fat is an important, but not an exclusive factor. In studies relating to populations, the contribution of fat to the total energy intake and total energy intake itself are only moderately correlated. First results of prospective studies have shown that the intake of food of high energy density is prospectively associated with the development of obesity.

On the other hand , the results of a meta-analysis of weight-reduction studies suggest that in individuals of normal weight in an ad libitum situation, a reduction of the proportion of fat in the total energy supply does not reduce weight. Reliable conclusions on the effects of a strongly increased proportion of fat in the total energy intake, typical e.g. of Atkins diet, on the long-term development of body weight cannot be drawn. Physical activity is another important factor of the energy balance which varies greatly among individuals.

Given a high-energy diet and low physical activity, it could be possible that much dietary energy is already ingested before the mechanisms of satiation take effect so that the energy balance turns positive. To reduce the energy density including fat content of the diets and at the same time increase physical activity therefore remains a primary aim of public health policy.

Keywords: Obesity / development / fat intake / energy balance / physical activity / epidemiological studies

Sie finden den Artikel in deutscher Sprache in Ernährungs-Umschau 01/05 ab Seite 4.