Q: I heard that some people with “normal” weight or BMI actually have too much body fat that puts them at risk for chronic disease. Is that true, and if so, how would you know?
A: Yes, it is true. Some people have weight that falls within recommended ranges for body mass index (BMI), but a “healthy” BMI for any particular height often covers a range of about 30 pounds. So it is possible to be in the healthy range, but have too much of that weight as body fat, especially if you’ve lost muscle with age, illness or inactivity. Emerging research shows that this problem, called “metabolically obese normal weight” (MONW) or “normal weight obesity,” affects at least 25 percent of U.S. adults who have normal BMI. Although these people do not face health risks as great as people who are classified as obese, their rate of heart disease deaths and overall mortality rate are increased compared to people with a healthier body composition. People with excess body fat in the abdomen seem especially at increased risk, because this fat is most metabolically active. It is linked with insulin resistance and promoting a chronic, low-grade inflammation throughout the body. In a recent study that followed about 3,000 women for five years, those with more fat deep in the abdomen (visceral fat) were more likely to have a a heart attack or stroke or to develop cancer compared to the women with less visceral fat. These women all received computed tomography (CT) scans, a specialized type of X-ray that provides more detailed images of body structures than standard X-rays. Outside of scans like this, it’s difficult to identify excess visceral fat specifically, but one simple indicator of abdominal fat is your waist size. Use a tape measure and compare your measurement to the American Institute for Cancer Research and the World Health Organization recommendation to aim for waist size no larger than 37 inches in men or 31.5 inches in women. If despite a normal BMI, you’ve been gaining weight or if blood tests show elevations of triglycerides, blood sugar or hsCRP (high-sensitivity C-reactive protein), excess body fat may be at least partly responsible. Discuss with your health care provider whether a check of your body fat level with a health care or fitness professional trained in measuring body composition might be helpful. If you do have a waist measure above the healthy range or other signs of excess body fat, focus on getting moderate physical activity every day and use strength-training exercise to minimize loss of muscle tissue. At the same time, cut back on calorie-laden beverages; eat healthfully with meals centered around vegetables, fruits, whole grains and beans; and make sure that portion sizes satisfy hunger but don’t leave you stuffed. These steps may add up to help you lose a few pounds or waistline inches. After four to six weeks, measure your waist and check to see if blood sugar and triglycerides have improved.