Energy balance and cancers

Energy balance results from the exact equilibrium between caloric intake an d caloric expenditure. A caloric intake larger than caloric expenditure res ults in overweight, even obesity, but other determinants, like hormonal dys function and/or genetic traits may play a part in obesity syndrome. Obesity , and even overweight, have been recognized as risk factors for the develop ment of cancers. Human epidemiological studies, which have tended to establ ish the nature of the relationship between energy balance and cancer, are s ummarized first, with the influence of the various factors which act both o n obesity and on cancer risk. Among these factors are the macronutrients re sponsible for the caloric intake, and some lifestyle factors (physical acti vity, drinking habits and tobacco use). Second, the animal studies help to distinguish between different relevant factors, and to understand some of t he underlying mechanisms. However, the insulin-resistance syndrome, which a ppears to underlie the relationship between obesity and hormone-dependent c ancers, and possibly colon cancer, is only relevant to human physiology bec ause hormonal alterations are part of it. Prevention of hyperinsulinemia, i nsulin resistance and the accompanying visceral obesity appears to be a maj or public health task for the prevention of cancers. (C) 1999 Lippincott Wi lliams & Wilkins.