Obese people are thought to be at higher risk of so called ''fat cancers,'' including breast and colon cancers.
A separate report also out Friday also shows obesity rates worldwide have doubled in the last three decades, especially in the west.
Medical experts say changing diets and exercise routines are making people unhealthier, and in turn making them prone to such diseases as cancer.
Also, the World Health Organization is urging all nations do something about overeating and poor health habits.
The WHO recommends two-and-a-half hours of moderate exercise a week for reducing the risk of breast and colon cancers.