Weight loss surgery can control diabetes and heart disease.
But new studies show it also dramatically reduces cancer deaths, too, further tightening the obesity-cancer link.
Day by day, experts are learning what too much body fat does.
"It's not just like some sort of storage tub full of margarine," says Dr. Richard Bleicher, a breast cancer surgeon at Fox Chase Cancer Center.
Dr. Bleicher of Fox Chase Cancer Center says breast cancer was the first cancer tied to obesity.
However, that list keeps growing.
"Gall bladder cancer, uterine cancer, ovarian cancer, esophageal cancer, and many, many more," he says,
In fact, the National Cancer Institute says obesity raises the risk of 13 cancers: thyroid, breast, liver, gallbladder, upper stomach, pancreatic, colorectal, ovarian, endometrial, kidney, multiple myeloma, esophageal, and meningioma (lining of the brain and spinal cord).
Bariatric surgeon Rohit Soans of Temple Health says fat contributes in several ways.
"One of the big hormones that it produces is estrogen. Estrogen is directly linked in a lot of gynecological cancers," says Dr. Soans.
And it fuels breast cancer in men, as well as women.
"The heavier we get, the higher our estrogen levels," says Dr. Bleicher.
The second mechanism raising cancer risks is the increased level of insulin and insulin-like growth factors obese people have.
"Insulin is carcinogenic, and it can increase the rates of colon cancer, kidney cancer, prostate cancer," says Dr. Soans.
And there's a third mechanism:
"There's a lot of inflammatory things that are circulating in the body when an individual becomes obese, actually put out by the body fat," says Dr. Bleicher.
Those harm cells over time, helping some grow abnormally.
Dr. Bleicher says obesity also lowers survival after breast cancer.
The two surgeons say the full role of obesity in cancer isn't known yet, but it is clear treating it is important.
"Women that got bariatric surgery have a near 60% reduction in developing first-time gynecological cancers, including breast cancer," says Dr. Soans.
Dr. Bleicher adds, "If we can maintain a healthy body weight, we're all better off."
Dr. Soans notes that many obesity-related cancers are rising among people in their 30s and 40s, where obesity rates are so troublesome.