CALORIES AND EXERCISE AS MODIFIERS OF CANCER RISK

We can observe that a number of chronic diseases are associated with obesity and a fat-rich diet and we can observe that a sedentary lifestyle is associated with an increased risk of some cancers. But why are some people obese and some lean and muscular? Why do these people eat different diets and why do some people exercise and other people live a sedentary life? Weight loss induced by food restriction in animals seems to have a protective effect on the development of cancer, review given by Kritchevsky (1991). However, we do not know for sure about the mechanisms involved and the question of causality remains a guessing game in which we accumulate circumstantial evidence but where proofs are hard to come by.