International, multidisciplinary biomedical research in the field of nutrition and cancer has led to the recognition that the traditional Western total fat intake of about 40% calories constitutes a major risk factor for cancer of the postmenopausal breast, distal colon, pancreas, ovary, endometrium, and probably prostate. The underlying complex mechanisms have been sketched out, justifying public health promotion activities involving reduction of fat intake to 20 to 25% of calories, facilitated by the deliberate marketing of low-fat products by the food industries.