Adiposity and Cancer Risk

Obesity is a risk factor for several cancers, including colorectal cancer (CRC). I and my colleagues investigated adulthood weight change and body fat distribution and its change in relation to CRC risk in the Nurses’ Health Study and Health Professionals Follow-up Study. We also identified distinct trajectories of body fatness across the lifespan using a group-based modeling approach and then compared cancer risk across these trajectories. We found that weight gain from early adulthood to baseline was associated with an increased risk of CRC, whereas weight loss was associated with a lower risk. The association was stronger in men than in women. High waist circumference, hip circumference and waist-to-hip ratio were all associated with a higher risk of CRC in men, even after adjusting for body mass index. The associations were weaker in women. Ten-year gain of waist circumference, independent of weight change, was positively associated with CRC risk in men, but not in women. We identified 5 distinct adiposity trajectories across the lifespan: lean-stable, lean-moderate increase, lean-marked increase, medium-stable, and heavy-marked increase. Compared to women in the lean-stable group, those in the lean-marked increase and heavy-marked increase groups had a higher risk of esophageal adenocarcinoma and cancers of the colorectum, pancreas, kidney, and endometrium. Postmenopausal breast cancer risk was inversely associated with early-life adiposity, but was positively associated with late-life adiposity. In men, increased body fatness at any life period was associated with a higher risk of esophageal adenocarcinoma and colorectal cancer; compared to men in the lean-stable group, those in the heavy-marked increase group had a higher risk of pancreatic cancer, but lower risk of advanced prostate cancer. The trajectory-cancer associations were generally stronger for non-smokers and women who did not use menopausal hormone therapy. In conclusion, weight gain from early to middle adulthood was positively, and weight loss was negatively associated with CRC risk. Abdominal adiposity was positively associated with CRC risk and this association was stronger and independent of overall obesity in men than in women. Adiposity trajectories throughout life were associated with cancer risk and the pattern of associations varied by sex and cancer site.