Hypotheses regarding caloric intake in cancer development

The epidemiologic evidence on fats as related to cancer has until recently been equivocal. Some studies showed an inhibitory effect, some showed no effect, and a few showed a reduction in risk. More recently, however, epidemiologic inquiries have suggested that fats may be associated with increased risk of cancer of the breast, prostate, cervix, colon, rectum, larynx, and lung. The relationship is not a simple one. There is evidence that a high level of total calories ingested, regardless of whether the source is fats, carbohydrates, or proteins, increases risk. Still other studies suggest that calorie expenditure may be the important fact. Thus, obesity, derived from whatever source, may be etiologically related to some cancers. Fats being a potentially important contributor to obesity over the long term, may in this way increase risk.