OBESITY, FAT INTAKE, ENERGY-BALANCE, EXERCISE AND CANCER RISK A REVIEW

The literature on obesity, fat intake, energy balance and exercise is reviewed with respect to cancer risk in man. Animal experiments in the field are analyzed to find support for the epidemiological observatio ns. The problems involved in the interpretation of the human and anima l data are discussed and it is attempted to extract the essence of the present body of knowledge. No doubt obesity is associated with certai n cancers but a causal relationship is not fully established. Exercise to a moderate degree for prolonged periods of time evidently confers a decreased risk of some cancers. Causality is difficult to establish in human observations but animal experiments make such a relation appe ar very Likely. Since a fat-rich diet (in man) is usually a diet relat ively poor in fruits and vegetables it is difficult to ascribe an incr eased cancer risk on a fat-rich diet to the intake of fat alone as a s hortage in the intake of fruits and vegetables may well be an importan t factor. Again animal experiments generally support the idea that fat is a promoter for a number of experimental cancers. The type of fat i s probably important although some controversies still exist concernin g the relative effect of the different types of fatty acids.