Obesity is on its way to being deadlier than smoking as a cause of cancer, a leading researcher said Friday. Being obese is currently associated with about 14 percent of cancer deaths in men and 20 percent in women, compared with about 30 percent each for smoking, Dr. Walter C. Willett of the Harvard School of Public Health, told the annual meeting of the American Association for the Advancement of Science...
 
...Overall, Willett estimated 30 percent to 35 percent of cancers are due to nutritional factors, much of it to obesity.

In men, an average weight gain of 33 pounds increased the risk of esophageal cancer by 52 percent, thyroid cancer by 33 percent, and colon and kidney cancers each by 24 percent, the research found.

In women, a weight gain of 29 pounds increased the risk of cancer in the uterus and gall bladder by nearly 60 percent, esophagus by 51 percent and kidney by 34 percent, the study said...

..."One of the hypotheses is that the presence of excess fat cells could affect the levels of hormones in your body," Renehan said. "At a cellular level, that may favor the development of tumors in humans."

Because many studies have found that fatter people are more likely to get cancer, experts often recommend losing weight to reduce cancer risk.

"The simple message is that, if you manage to keep a healthy body weight, you will have a lower risk of developing cancer," said Ed Yong, of Cancer Research United Kingdom.