Sunday, July 27, 2008

All Body Fat Is Not the Same

All Body Fat Is Not the Same
by Karen Collins, MS, RD, CDN, American Institute for Cancer Research

A new study takes the well-established link between overweight and increased risk of colon cancer one step further—suggesting that one particular type of body fat may be a major culprit.

Compared to fat around the hips and thighs, fat located around the waistline is more strongly associated with health risks like heart disease, diabetes and certain cancers. However, all waistline fat may not be the same. Researchers now express much greater concern about visceral fat tissue—the fat that accumulates in and around abdominal organs such as the liver. These fat cells, according to emerging science, are likely more harmful than those found in subcutaneous fat, the fat found just under the skin.

Abdominal fatness increases risk of some cancers more than others, colon cancer in particular. A study published this March looked specifically at the link between the two types of abdominal fat and potential precancerous growths. Involving 200 men and women undergoing both a colonoscopy to screen for abnormal growths in the colon and a computed tomography scan of their abdomen and pelvis, the study separately measured the two different types of abdominal fat.

Results showed that subjects who had abnormal growths had significantly larger waists than subjects without them; however, it was visceral fat that was most strongly linked to the potentially cancerous growths. People with the most visceral fat were more than four times as likely to have growths compared to those with the least visceral fat.

Why would visceral fat pose a greater health risk than other body fat? For starters, research shows that visceral fat is directly related to inflammation throughout the body, which has been linked to cancer and heart disease. Studies suggest that visceral fat tissue contains more macrophages, a type of immune cell that produces cytokines, a hormone-like protein implicated in chronic inflammation. Cytokines may also increase cancer risk in several other ways: They can increase oxidative stress and boost free radical production (creating DNA damage which could spark cancer development) and they can disturb insulin function (impairing both sugar and fat metabolism).

The fat cells themselves secrete a variety of hormones. One called resistin impairs the action of insulin. Scientists theorize this may be part of the reason that excess body fat is associated with a condition called “insulin resistance” in which ever-higher amounts of insulin are needed to control blood sugar. These higher insulin levels may promote some types of cancer and other health problems.

Without the help of a CT scan, most of us won’t be able to tell if a growing waistline is thanks to visceral or subcutaneous fat. Instead focus on meeting current recommended guidelines for a healthy waist circumference. According to the American Institute for Cancer Research, cancer risk increases at waist sizes greater than 31.5 inches for women and 37 inches for men.

In addition, maintaining a healthy weight is also essential. Some research suggests that weight loss can reduce production of inflammatory cytokines and increase expression of anti-inflammatory ones. Physical activity, which is key to weight control, may also have addition effects, including helping insulin to work more effectively.

Article Provided by American Institute of Cancer Research

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