The High Cost of Physical Inactivity

January 12, 2006—Slimming down after the holidays could be a lifesaver. Two new studies (published in the Journal of Applied Physiology [2005;99:1613–18] and in the Lancet [2005;366:1640–49]) point to the importance of exercise in reducing abdominal fat, and the health benefits that such weight loss may ultimately provide.

Overweight people are at increased risk for cardiovascular disease, diabetes, and other health conditions. The amount of excess weight is a critical factor, but so is the location. Several studies have documented a specific relationship between a big belly and increased disease risk. Dietary modification, particularly after the indulgences of the holiday season, is an effective way keep off excess weight. And so is exercise. But how much exercise do you need to keep the fat off your middle?

The first study sought to answer this question by recruiting 175 sedentary, overweight men and women with mild to moderate dyslipidemia (high total and LDL cholesterol, low HDL cholesterol). Participants were randomly assigned to a control group (no exercise program) for six months, or to one of three exercise groups for eight months: (1) low amount, moderate intensity, equivalent to walking 12 miles per week; (2) low amount, vigorous intensity, equivalent to jogging 12 miles per week; or (3) high amount, vigorous intensity, equivalent to jogging 20 miles per week. Computed tomography scans were used to assess abdominal fat.

People in the control group gained fat around the middle during the study period. Those exercising the equivalent of 12 miles per week, at either intensity, prevented significant accumulation of belly fat. The highest amount of exercise resulted in a loss of belly fat. The authors concluded that a modest exercise program, consistent with recommendations from the Centers for Disease Control and the American College of Sports Medicine, prevented significant increases in abdominal fat. Slightly exceeding these exercise recommendations led to significant decreases in belly fat without any changes in caloric intake.

The take-home message: Exercise regularly and prevent fat accumulation. Exercise more vigorously and lose weight.

Losing the weight around the middle is not just about looking and feeling good. It could save your life, as the waist-to-hip ratio turns out to be a good indicator of heart-attack risk.

A large case-control study explored the relationship between overweight—as assessed by body mass, waist, and hip circumferences, and waist-to-hip ratio—to heart attack (myocardial infarction). (A case-control study is a type of population study in which people with a condition, such as heart attack, are compared to people without that condition.) The study included 27,098 people in 52 countries (12,461 cases and 14,637 controls) representing several major ethnic groups.

While the authors found the expected relationship between body mass index (BMI) and heart attack, the risk posed by an out-of-line waist-to-hip ratio was much more dramatic. In other words, the larger the belly in relation to the hips, the greater the risk of heart attack. Their results suggest that the waist-to-hip ratio is a better indicator of heart attack risk (at least insofar as that risk is attributable to obesity) than the more traditional BMI measure.

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Jeremy Appleton, ND, CNS, is a licensed naturopathic physician, certified nutrition specialist, and published author. Dr. Appleton was the Nutrition Department Chair at the National College of Naturopathic Medicine, has served on the faculty at Bastyr University of Natural Health Sciences, and is a former Healthnotes Senior Science Editor and a founding contributor to Healthnotes Newswire. He has worked extensively in scientific and regulatory affairs in the supplement industry and is now a consultant through his company Praxis Natural Products Consulting and Wellness Services.

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