Fat intake, obesity, and cancer of the breast and endometrium.

Many studies indicate that obesity is associated with postmenopausal breast cancer and cancer of the endometrium. The mechanisms by which obesity contributes to cancer risk is not known, although increases in serum estrone from delta 4-androstenedione by the adipose tissue have been implicated in postmenopausal women. Blood estrogens increase with the degree of obesity and aging. In animal experiments the confounding of high fat, low carbohydrate, and high calorie diets needs to be defined. The effects of diet on estrogen metabolism; the relationship of fatty acids from animal, vegetable, and marine sources to tumor formation; and the mechanisms by which energy intake influences cancer risk need to be precisely defined. Any estimate of the contribution of heredity to the burden of human cancer is impossible until we have a better understanding of genetic and environmental interactions.