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depends largely on menopausal status. Interestingly, before menopause obese

women have a lower risk of developing breast cancer than women of healthy

weight. However, after menopause, obese women jump to twice the risk.

Estrogen seems to be the culprit. Before menopause, the ovaries are the

primary source of estrogen, but fatty tissue also produces it. After

menopause, when ovaries stop producing this hormone, fatty tissue

becomes the main estrogen source. Consequently, estrogen levels in post-

menopausal, heavy women can be twice as high as that of their lean counter-

parts. High estrogen levels after menopause seem to play an important role

in the development of breast cancer, but again, researchers don’t know why.

Colon (Colorectal)

Cancer

Although men can develop breast cancer, the rates are

obviously many times higher in women. But colon

cancer (which can also develop in women) occurs at

much higher rates in men. The colon is commonly

referred to as the large intestine, and men with a BMI

over 25 have an increased risk of developing cancer in this organ. Study after

study consistently reports such findings, but like so much of what we’ve dis-

cussed so far, the medical community still can’t say precisely why.

Researchers have proposed a number of ideas concerning obesity’s effect

on colon-cancer risk. One major theory suggests that high levels of insulin

in obese people may promote the growth of tumors. Another theory con-

cerns diet. A diet low in fiber has also been linked to an increased risk of

colon cancer. Fiber is most plentiful in certain vegetables, fruits, legumes,

and whole grains. All of these foods also tend to be extremely healthy and

low in fat. Many people develop overweight and obesity at least in part

because of unhealthy diets. If the unhealthy diet that contributed to the

weight gain was also low in fiber (as most unhealthy diets are), could this be

62 / Health Issues Caused by Obesity