Energy Balance, Exercise, and Cancer Risk

Excess body weight is a risk factor for most cancers. Furthermore, obesity is associated with worsened prognosis after a cancer diagnosis and negatively affects the delivery of systemic therapy, contributes to morbidity of cancer treatment, and may raise the risk of second malignancies and comorbidities. However, an obesity paradox may be occurring in patients with cancer; this paradox has been observed when cancer patients with an elevated body mass index (BMI) have improved survival compared with normal-weight patients, and this has been observed in a variety of cancer patients. The reliance on BMI as a measure of body fatness has limitations in the cancer population; hence, the use of tools that directly measure body fat may be more predictive of cancer risk. Despite public health recommendations for achieving and maintaining a healthy weight for cancer prevention and survivorship, few studies have evaluated the effect of intentional body weight loss on cancer risk, although the evidence is suggestive of a relationship. Future research needs to elucidate if weight loss after a cancer diagnosis decreases the risk of recurrence and mortality, and if so, how much weight loss is needed. This review contains 4 figures, 1 table and 65 references Key words: body weight, cancer, interventions, lifestyle, morbidity, mortality, obesity, prevention, risk, sedentary, survivorship, weight loss