Dietary fat and obesity: lack of an important role*

Abstract

The percentage of dietary energy from fat has been suggested to be an important determinant of body fat, and this presumed effect has been used to promote low-fat diets. In short-term randomized trials, a small reduction in body weight is typically seen in individuals randomized to diets with a lower percentage of calories from fat. However, in trials lasting for 1 year or longer, fat consumption within the range of 18-40% of energy had consistently had little if any effect on body fatness. The weighted mean difference was -0.25 kg overall and +1.8 kg for trials with a control group that received a comparable intensity intervention (i.e. less weight loss on the low-fat diets). Moreover, in the USA and other affluent countries, a substantial decline in the percentage of energy from fat during the past two decades has corresponded with a massive increase in obesity. Diets high in fat do not account for the high prevalence of excess body fat in Western countries; red uctions in the percentage of energy from fat will have no important benefits and could further exacerbate this problem. Keywords: adiposity; diet; fat; obesity; overweight