The Doctor's Diet: Dr. Travis Stork's STAT Program to Help You Lose Weight & Restore Your Health (54 page)

Our bodies are made up of trillions of cells that are constantly growing and dividing. Sometimes—because of genetic mutations, environmental damage, or other reasons—cells can begin to grow and spread abnormally. When this growth is not stopped or controlled, cancer develops.

Some people are way more apt to get cancer than others. Smokers, for example, have a very high risk of getting lung cancer because cigarette smoke contains at least 69 known carcinogens.

In animal studies, scientists see that compared with normal-weight animals, tumors in fat animals grow faster and larger, spread more quickly, and are more resistant to treatment. Observational studies find similar trends in people: overweight and obese people get more cancer, their cancer gets worse, and they are more likely to die from it than people of normal weight.

Why is this? Why are people who are overweight or obese more likely to get cancer than those whose weight is normal? Here are some of the reasons:

Extra weight equals extra estrogen.
Body fat produces estrogen, and estrogen fuels some kinds of cancer, such as estrogen-positive breast cancer and endometrial cancer. The more fat you have, the more estrogen you have in your blood.

Insulin resistance sets the stage for cancer development and tumor growth.
Overweight and obese people are likely to have insulin resistance, which we talked about back in the section on blood sugar. If you are insulin resistant, your blood is likely to have high levels of insulin and a substance called insulin-like growth factor-1 (IGF-1). Both insulin and IGF-1 seem to promote the growth of certain kinds of tumors because they help regulate cell division.

Fat cells produce cancer-spurring proteins.
Your body’s fat cells—especially the fat cells that take up residence in your belly—release proteins known as adipokines, which can play a part in cell growth. People with excess belly fat tend to have lower levels of the protein adiponectin, which helps prevent the growth of cancer cells. And they
are likely to have higher levels of leptin, which seems to promote the proliferation of cancer cells.

Fat may turn cancer genes “on.”
Only about 5 percent of cancers are related to genetic mutations. But not everyone who has certain cancer-causing genetic mutations goes on to develop cancer. Scientists believe certain factors (such as environmental toxins, diet, body fat, smoking, and others) may have the ability to “turn on” some cancer genes. It appears that having excess body fat seems to contribute to the turning on of genes linked to cancer in people with a genetic predisposition.

Excess weight boosts inflammation.
As we discussed earlier in the book, having extra body weight and body fat—especially belly fat—turns up the heat on chronic systemic inflammation, which appears to contribute to the development of some kinds of cancer.

Inactivity contributes, too.
People who are overweight or obese are less likely than healthy-weight folks to get enough exercise. Since exercise helps ward off cancer, inactivity is believed to be one of the links in the cancer-weight connection. Activity spurs the action of several cancer-fighting events: it lowers inflammation, boosts immunity, lowers levels of pro-cancer hormones such as estrogen in the blood, helps regulate leptin (known as the “weight hormone”), and improves blood sugar and insulin resistance.

Cancer takes a long time to develop. As many as 10 years can go by before the early cellular changes of cancer cause signs and symptoms that
can be detected by people and their doctors. So it’s a little hard for researchers to make surefire connections between weight loss and reduction of cancer risk. However, there is a fair amount of evidence that making changes like the ones in The Doctor’s Diet can bring down cancer risk.

For example, a large 2006 study published in the
Journal of the American Medical Association
found that women who lost 4 to 11 pounds after menopause had a more than 20 percent lower risk of breast cancer compared to women whose weight did not change. Not all studies have shown this same benefit, but heck, it’s evidence enough for me to encourage all the women I know to try to lose extra pounds.