Obesity and cancer third most important risk factor for cancer in the United States, just behind tobacco and diet (see Figure). Obesity is the source of about 15% of all preventable cancers. In 2018, Chinese researchers performed a systematic review and comprehensive quantitative meta‐analysis of cohort studies reporting body mass index (BMI) and the risk of 23 cancer types, providing epidemiological evidence supporting the association between BMI and cancer risk. The strongest positive association between BMI and cancer risk was found among patients in North America. The mechanisms by which obesity may increase the risk of cancer are not well understood, but it
Alcohol and cancer risk of stomach cancer in heavy smokers." A Taiwanese study concluded, "…cigarette smoking may play the most harmful role in the initial development of gastric cancer, and that drinking alcohol may promote the process." A Norwegian study found that, "No statistically significant associations between various degrees of exposure to alcohol and risk of gastric cancer was revealed, but combined high use of cigarettes (>20/day) and alcohol (>5 occasions/14 days) increased the risk of noncardia gastric cancer nearly 5-fold (HR = 4.90 [95% CI = 1.90–12.62]), compared to nonusers." Alcohol has been identified as a risk factor for endometrial cancer. Data