Obesity and Cancer

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CUDA: Obesity increases the risk for cancers of the breast, uterus, kidney, colon, pancreas, esophagus and gallbladder - and sometimes quite substantially---that's according to the American Institute for Cancer Research. Joe Nadeau studies the link between cancer and obesity at Case Western Reserve University.

NADEAU: This relationship is very strong for many cancers - not for all cancers. And why for some and not for others is not clear.

CUDA: There doesn't appear to be any link between obesity and lung cancer for example - yet obese people get cancer of the esophagus at a rate 8 times that of people who maintain a healthy weight. In esophageal cancers, doctors think there may be a relatively simple explanation -pressure on the abdomen caused by excess weight leads to heartburn -the acid damages the cells and causes cancer.
The relationship between other cancers and obesity is less direct. The prevailing theories are that it is the result of a high-fat diet, changes that occur in the fat cells themselves, or both. Researchers once thought that -aside from contributing to excess weight - fat cells - also known as adipose tissue - were harmless storehouses of excess calories. But they now know they are capable of releasing chemicals that can do the body harm - and potentially cause cancer.

KRONIGER: What we think is going on is that when you become more obese the white adipose tissue actually secretes substances and it causes more inflammation. We think the bottom line is inflammation.

CUDA: That's Colleen Kroniger, another obesity researcher and one of Joe Nadeau's colleagues at Case. She says a little inflammation is a good thing- it's the body's way of protecting us from infections. But obesity puts people in a state of constant inflammation, and that can have harmful effects. High-fat, high-sugar foods can damage the body's cells and increase inflammation, while also making us fat. What's more, she says, the location of the fat cells creating the inflammation seems to be important, especially if its belly fat.

KRONIGER: When you have obesity around your abdominal cavity, it's wrapped around your liver, it's wrapped around your intestines - so those organs are very close to the source of those chemicals and that causes problems.

CUDA: But for obesity researchers, one question still looms large: if obesity causes cancer, then how come some obese people get cancer and others don't?

In Joe Nadeau's lab, they use two strains of mice that have very different metabolisms as a model for what might be going on in humans.

Both strains are fed a high fat diet, similar to a typical fast-food meal, and allowed to eat as much as they want. One strain of mice stays thin - even though they eat 40 percent more than the other mice and aren't very active. The other strain becomes morbidly obese despite eating less and exercising more. And what's more - after a year, the obese mice get liver cancer, and the thin mice don't . These thin mice appear to not only be genetically programmed to stay lean, but also protected from liver cancer.

The group also looked at colon cancer, but this time they found that both the thin and obese mice got colon cancer after eating a high fat diet - indicating that diet, not genetics was the cancer causing agent. Furthermore, Nadeau says they found that the type of fat in the diet makes a difference.

NADEAU: Coconut oil fats, corn oil fats - those are chemically specific fats - will promote cancer development. Fish oils are much less potent in this way, in fact, they may even be protective.

CUDA: Researchers also learned that the timing of our eating habits can change the outcome. Adopting a low fat diet even after a long period of gorging can cause a developing cancer to disappear. Good news for those of us switching to healthier lifestyles later in life. The bad news from the mice study is that if the pattern is reversed and a switch is made from a low fat diet to one full of burgers and fries, you die from a heart attack before you have time to develop liver cancer.

Nadeau sand Kroniger say the bottom line is this: every individual has a different cancer risk that is determined by their genetics and their lifestyle - researchers are still trying to understand how those factors interact in the hope that one day they'll be able to offer personalized solutions. But for now, the best advice for reducing your cancer risk is applicable to everyone: stay thin, eat healthy, and exercise.

Gretchen Cuda 90.3

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