A study recently conducted in Great Britain found that a high body mass index (BMI) places individuals in a risk zone for certain types of cancer. The risk varied depending on the type of cancer, but for 17 out of 22 types of cancer there was a positive association between excess weight and the risk for cancer. BMI is a way to measure the amount of fat in the body, and is calculated by comparing a persons weight to their height. This measurement is used to determine if an individual is overweight or has a problem with obesity. So one way to decrease the risk of cancer is to maintain normal body weight.
Source: The Lancet, Aug. 30 2014, doi:10.1016/SO140-6736(14)60892-8