Socioeconomic status and obesity.

Two recent developments have thrown into bold relief the importance of environmental forces in determining the prevalence of human obesity. The first is genetic studies that estimate the heritability of human obesity at no more than 33%. The second is the 33% increase in the prevalence of obesity in the USA during the past decade. The importance of the environment in influencing obesity is matched only by the extent of our ignorance of how it exerts its effects and of how we may favourably alter them. The most thoroughly studied measure of environmental influences is socioeconomic status. Among women in developed societies socioeconomic status is strongly (negatively) correlated with the prevalence of obesity: the lower the social class the more the obesity. Prospective studies have shown that this correlation reflects, in part, causation: socioeconomic status helps to determine the prevalence of obesity and thinness. Likewise, the presence of obesity helps to determine socioeconomic status. In developing societies there is also a strong relationship between socioeconomic status and obesity, but it is a positive one: the higher the socioeconomic status the more the obesity. Unfortunately, we know of few other social determinants of obesity and studies on the social determinants of this disorder are desperately needed.