AICR eNews May 2012 | Issue 70
Understanding how body fat affects your health can help you better manage your weight, which will in turn lower your cancer risk and offer a range of other health benefits. To get an update on the latest findings, AICR spoke to a leading researcher in this field, Anne McTiernan, MD, PhD, Director of the Prevention Center at the Fred Hutchinson Cancer Research Center in Seattle.
“Until recently, it was widely thought that people are born with a set number of fat cells that shrink and expand, depending on our diet and physical activity,” Dr. McTiernan said. “Now we realize that fat tissue is more complex than this,” she says.
Moving and Losing Fat Go Together
Dr. McTiernan is studying the effects of increased physical activity and weight loss on reducing several risk factors for cancer. In one study, she found that overweight post-menopausal women who exercised for 45 minutes, five days a week, reduced unhealthy body fat. The physical activity also lowered their estrogen and testosterone levels. High amounts of these hormones in the body can contribute to cancer risk.
In another study, Dr. McTiernan found that exercising six days a week led to significant fat loss in both men and women and a lowered risk of some colon cancer risk factors in men.
AICR: What happens to fat cells when we exercise?
Dr. McTiernan: Exercise alone doesn't have a large impact on fat tissue, but does decrease it somewhat. Physical activity plus eating a healthy, mostly plant-based diet is the key to preventing weight gain, according to AICR's expert report.
AICR: What role do fat cells play in cancer risk?
Dr. McTiernan: Inflammation-promoting proteins and estrogen and can lead to insulin levels that are too high. These are factors that can increase cancer risk.
AICR: How are fat cells (especially those around the waist) involved in increasing hormone production?
Dr. McTiernan: The fat in the abdominal area, around the organs, is thought to be most active in promoting elevated insulin levels and lipid disorders (such as high cholesterol and high levels of triglycerides, a type of fat in the blood), as well as excess inflammation.
AICR: What are fat cells' role in inflammation?
Dr. McTiernan: Too much body fat produces large amounts of inflammation-promoting proteins (cytokines) that prompt the liver to make the substance C-reactive protein (CRP), which gets released into the bloodstream. Consistently high inflammation levels, indicated by the presence of CRP in blood tests, are common signs of higher risk for cancer, diabetes and heart disease.
AICR: Why do our calorie needs diminish with age?
Dr. McTiernan: Older people are less active and therefore their muscle/bone mass decreases, all of which reduce metabolic rates, leading to lower calorie needs.
AICR: Is weight loss important for older people (age 75+)?
Dr. McTiernan: Weight loss in older persons improves several health aspects including reducing risk for developing diabetes. Weight loss through just dieting, however, reduces lean mass and bone mass, so exercise is very important in this age group because it can the slow loss of muscle and bone that would otherwise happen with calorie restriction.
AICR: Is any progress being made in halting the obesity epidemic?
Dr. McTiernan: There is not enough progress. We need to educate the public, businesses, public partnerships and health care communities and come together to solve this problem.