The Medicine Cabinet: Ask the Harvard Experts
By Howard LeWine, M.D.
Q: I recently met my new doctor. He was worried about my waist size. I’ve always had a big belly but I have never been overweight. What’s more important: body weight or waist size?
A: That’s terrific that your doctor focused on your waist size. Even though you are not overweight, having a large belly raises your risk of developing heart disease. Mounting evidence suggests that waist circumference is a better gauge of heart disease risk than body mass index (BMI).
A big belly — what doctors call central or abdominal obesity — signals the presence of visceral fat. It’s the fat that surrounds your internal organs. In general, as your waistline increases, so does your visceral fat.
Visceral fat is metabolically active, which means it produces hormones and other factors that promote inflammation. Inflammation plays a key role in the accumulation of cholesterol-laden plaque inside the arteries, which may explain the link between visceral fat and cardiovascular problems.
Calculating your waist-to-hip ratio is an easy way to find out if you may have too much visceral fat. Use a tape measure to get a reading on your waist size. Exhale and wrap the tape around your bare abdomen just above your navel (belly button). Don’t suck in your gut or pull the tape tight enough to squeeze the area.
Next put the tape measure around the widest part of your buttocks. Keep the tape measure level. Now divide your waist size by your hip size to calculate your waist-to-hip ratio. Central obesity is defined as having a waist-to-hip ratio of greater than 1.0 for men or greater than 0.9 for women.
Certain people are more likely to accumulate visceral fat, which is governed by genetic, ethnic and gender differences. For example, natives of India and South Asia have a higher-than-average propensity for abdominal obesity. And white men and black women tend to accumulate more visceral fat compared with black men and white women.
Fortunately, with diet and exercise we tend to lose visceral fat first, before fat underneath our skin. That’s why shedding as little as 7 percent of your excess weight helps lower heart disease risk: the most dangerous fat goes first.
Howard LeWine, M.D., is an internist at Brigham and Women’s Hospital in Boston and assistant professor at Harvard Medical School. For additional consumer health information, please visit www.health.harvard.edu.