From the AICR Newsletter #117, Fall 2012
Anne McTiernan, MD, PhD
Studying the biology of fat cells is helping scientists better understand weight gain, weight loss and how being overweight or obese increases cancer risk. In this article, a leading researcher discusses how fat cells work.
Understanding how body fat actively affects your health can help you better manage your weight for lower cancer risk and other health benefits.
"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," says Anne McTiernan, MD, PhD, Director of the Prevention Center at the Fred Hutchinson Cancer Research Center in Seattle. “Now we realize that fat tissue is more complex than this,” she says.
Dr. McTiernan is studying the effects that increased physical activity and weight loss have on reducing the risk factors for breast 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 reduced some colon cancer risk factors in men.
AICR: Is weight loss important for older people (age 75+)?
Dr. McTiernan: Weight loss in older persons improves several aspects of health, including reducing risk for developing diabetes. Weight loss through dieting alone, however, also reduces lean muscle and bone mass, so exercise is very important in this age group because it can slow loss of muscle and bone that would otherwise happen with calorie restriction.
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: Fat cells produce inflammation-promoting proteins and the hormone estrogen and can lead to insulin levels that are too high. These are factors that can increase cancer risk.
AICR: How are fat cells active (especially those around the waist) in increasing hormone production?
Dr. McTiernan: The fat in the abdominal area, around the organs, is thought to be most active in producing too much insulin and lipid disorders (such as high cholesterol and high levels of triglycerides, a type of fat in the blood), as well as excess inflammation. An overload of estrogen, however, is most likely to be made in the fat under the skin, anywhere in the body. So it's important to keep fat levels down regardless of where the body fat is located.
AICR: Why do our calorie needs diminish with age?
Dr. McTiernan: Older people are generally less active. In addition, their muscle/bone mass decrease, all of which reduce metabolic rates, leading to lower calorie needs.
AICR: What is the role of fat cells in inflammation?
Dr. McTiernan: Eating too much fat produces large amounts of inflammation-promoting proteins 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: Is any progress being made in halting the obesity epidemic?
Dr. McTiernan: There is not enough progress. We need to educate the public, business, public partnerships and the health care community and come together to solve this problem.
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