Lack of Muscle and Obesity Increase Cancer Risk

A study in the New England Journal of Medicine concludes that losing weight could prevent more than 90,000 deaths from cancer each year. That's one of every six cancer deaths in the United States.

Researchers at the American Cancer Society spent 16 years evaluating 900,000 people who were cancer-free when the study began in 1982. They found that excess fatmay account for 14 percent of all cancer deaths in men and 20 percent of those in women.

If you are overweight, this study should scare you into exercising more and eating less. This is the largest study ever on the association between obesity and cancer, and it is the most statistically significant. The study has more than 10 times greater statistical significance than the largest previous research on the topic.

This study agrees with most previous studies in that it shows that obesity is associated with increased risk for cancers of the breast, uterus, colon, rectum, kidney, esophagus, and gall bladder. In addition it brought new associations between obesity and cancers of the cervix, ovaries, multiple myeloma, non-Hodgkins lymphoma, pancreas, liver, and in men, the stomach and prostate.

Having too much fat causes cancer by causing you to have too much insulin like growth factor-1, a cancer promoting hormone. Insulin cannot do its job of driving sugar into cells until it first attached to hooks on cells called insulin receptors. When have too much fat inside cells, this causes the receptors to turn inwardly so they are not available to insulin. Since there are fewer docking sites for insulin, your cells so not respond to insulin as well, so your pancreas has to release far more insulin that usual to do the same job. High levels of insulin and insulin-like-growth factor-1 cause cells to grow much faster, and too much insulin like growth factor causes cells to grow so fast that they can become cancerous.

I think the researchers should have concluded that lack of muscle, rather than just having too much fat, causes cancer. Your body produces millions of cancer cells every day that you are alive. However, your immunity should be strong enough to search out every cancer cell and kill them before they can start growing and multiplying in your body. As you age, you lose your ability to kill cancer cells and germs, because of lack of muscle.

When a germ gets into your body, you must make cells and proteins called antibodies to kill these germs. However, antibodies and cells are made from protein and the only place that you can store extra protein is in muscles. When you have large muscles, you have a ready source of protein from muscles to make antibodies and cells. When you have small muscles, you have a very limited source of amino acids to make protein, and your immunity is often inadequate to kill germs.

In the same way, you need antibodies to control cancer cells, so with loss of protein stores in your muscles comes loss of antibodies and increased susceptibility to suffer cancer.

1) NEJM April 24, 2003.

Checked 9/1/08

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