Nutritional cancer risks derived from energy and fat.

Both animal and human studies indicate that increased caloric intake and increases in body weight and obesity are associated with increased risk of cancer of the breast, endometrium, ovaries, colon, rectum and prostate. Recent animal studies indicate that it is the total caloric intake, rather than the percent of fat in the diet, that is associated with tumorigenesis and carcinogenesis, and that tumor development depends on a complex interaction involving energy intake, energy expenditure, energy retention within the body (body fat vs lean body mass) and body size. Omega-3 fatty acids inhibit tumorigenesis and tumor growth in many cancer models in rodents. Exercise diminishes tumor formation in mice, rats and humans. Exercise delays mortality from all causes, and life-long exercise is associated with decreased cancers of the breast and reproductive system in women, and cancer of the colon in women and men.