Being overweight is a strong risk factor for developing diseases like typ 2 diabetes, heart disease and osteoarthritis, and most people are aware of this. Unfortunately, research data now also shows that a significant number of cancers are directly linked to an elevated BMI. Today the American CDC (Centers for Disease Control and prevention) released a report, that is commented in the paper JAMA, titled “Excessive Weight Gain, Obesity and Cancer. Opportunities for Clinical Intervention”. They have surveyed more than 1000 scientific studies and found correlations between weight gain/overweight/obesity and the following cancers: esophagus, gastric cardia, colon and rectum, liver, gallbladder, pancreas, corpus uteri, ovary, kidney, and thyroid; postmenopausal breast cancer; meningioma; and multiple myeloma.
CDC concludes that the above cancers in the USA represent 55% of all diagnosed cancer in women and 24% in men. They are also worried of the fact that the proportion of young people is increasing. The rest of the JAMA article reasons around the possibilities of primary weight gain prevention in society. Treatment of already established obesity is not mentioned, however the fact that bariatric surgery as a very effective method of decreasing cancer risk at least in women is well described, see here for an example.
In conclusion effective long term weight loss is not only about decreasing the risk of diabetes and heart disease, it is as much about avoiding cancers.