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Can you be normal weight and fat at the same time?
That’s the implication of a provocative recent report from the Mayo Clinic, which suggests that fat in your body can get you and your heart into trouble even if you don’t look fat and if the scale tells you you’re healthy.
The Mayo researchers, led by cardiologist Francisco Lopez-Jimenez, have coined a term for the phenomenon: normal weight obesity. In a study that looked at data from 6,171 Americans with normal body size, as measured by body mass index, those with a high percentage of body fat were at significantly greater risk of future heart problems than those with low amounts of fat. Their bodies “behave like they are obese, but they are not,” Dr. Lopez-Jimenez says.
Even some thin people could be at risk for health issues typically associated with individuals who are fat, Ron Winslow reports.
People don’t have to be overweight to have excess body fat. Instead, these people have a higher ratio of fat to muscle tissue than do people with low body fat. Indeed, even people of the same weight, or those with comparable body mass index, which factors together weight and height, can have different body-fat percentages.
Based on results of the nine-year study, as well as U.S. Census and obesity data, Dr. Lopez-Jimenez and his colleagues estimate that as many as 30 million Americans may fall into the normal-weight-obesity category, many of them unaware they may be at increased heart risk.
The study “drills down on a population where we’re making assumptions that everybody is healthy. It may well be that they’re not,” says Robert Eckel, an obesity and metabolic-syndrome expert at the University of Colorado, Denver, who wasn’t involved with the study.
But Dr. Eckel and other medical experts caution that the findings need to be validated with additional research. Big epidemiological studies such as the Mayo report are useful for spotting important trends and raising hypotheses for further inquiry. But they are not necessarily reliable for prescribing specific remedies for individual patients.
People can measure body fat at home with specialized scales, such as this model by Tanita, which pass a small electrical current through body tissue. Many health clubs offer body-fat assessments.
Indeed, Dr. Eckel says he doesn’t think the study’s results mean people should have their body fat measured to assess their cardiac risk. Generally, a little extra weight around the middle among normal weight people should be a sufficient wakeup call, other doctors say. More research is needed to determine whether reducing body fat percentage in such people would lower risk of heart disease.
Still, body-fat assessment is a common feature at many gyms. At Equinox Fitness Club, a national chain based in New York, members get a body-composition test as part of an initial assessment before they begin a training regimen. “This is a culture obsessed with weight, but very little attention is paid to the composition of that weight,” says Geralyn Coopersmith, an exercise physiologist and senior national manager for Equinox’s training program.
Among some of the Mayo Clinic study’s findings: High body fat among normal-weight men and women was associated with a nearly four-fold increase in the risk for metabolic syndrome—a cluster of abnormalities including elevated blood sugar and blood pressure. This syndrome is common among people who are obese and is an increasingly important precursor to diabetes and cardiovascular disease. For women, high body fat meant a heightened risk of being diagnosed with cardiovascular disease over the course of the study. Both men and women had a higher risk of abnormal cholesterol and men with high body fat were more likely to develop high blood pressure.
The research suggests that body mass index, or BMI, the tool doctors and researchers often use to determine whether a person is obese, may fall short in some cases as an indicator of good health. BMI is obtained by dividing your weight in kilograms by your height in meters squared. People with a BMI between 18.5 and 24.9—the range for the participants in the Mayo study—are considered to be normal weight under government guidelines. A BMI of 30 or higher indicates obesity, while people in the range from 25 to 29.9 are considered overweight. The overweight category in particular has generated controversy because many people who exercise regularly and are considered fit have BMIs above 25.
Fit Versus Fat
BMI, or body mass index, is a key indicator of healthy weight.
• Calculate by dividing your weight in kilograms by your height in meters squared. Or go to www.nhlbisupport.com/bmi for an online tool and plug in your particulars. Body fat can still be high, even when weight is healthy.
• Calculate body fat percentage using a process known as bioelectrical impedence analysis, which passes a small electrical current through body tissue. Specialized body fat bathroom scales for home use are available for purchase at drug stores or online, but offer varying levels of reliability. Skinfold tests are another technique. While some doctors may offer such tests, you’re more likely to find them at health clubs.
• Generally, body fat percentages over 25% for men and over 35% for women are considered high. Preferred targets are considerably lower. But there isn’t a professional consensus on an optimal level.
Dr. Lopez-Jimenez says that measuring body fat could help identify previously unappreciated risk in the normal-weight population. He likens the issue to cholesterol. Total cholesterol below 200 has long been considered a heart-healthy target, but research has also shown that people can have “healthy” total cholesterol but low levels of HDL, or good cholesterol, and high levels of LDL, or bad cholesterol, that put them at heightened risk for heart attacks.
Monika Sumpter, a 34-year-old training manager at Equinox Fitness in New York City, says she once weighed 170 pounds and had a body fat percentage of “a little over 30%,” a high reading. She says she lost 45 pounds with diet and some aerobic exercises, but reduced her body fat percentage only to about 25%. So, over the past 18 months, Ms. Sumpter says she added strength training and other exercise to her cardio workout. Although she has put 20 pounds back on, her body fat percentage is down to 14%, she says.
For consumers, conversations about body fat and body composition are more likely to happen during a workout with a personal trainer than at a doctor’s office during an examination. The test isn’t a widely accepted clinical measurement. And there isn’t a consensus among medical experts about what percentage of body fat is “normal” or what level indicates higher risk.
Some gyms have their own guidelines. At Equinox Fitness Club, trainers consider body composition and waist circumference—another indicator of body fat—more important in assessing fitness of many members than weight. The club’s Ms. Coopersmith says that, based on data from the American College of Sports Medicine and the American Council on Exercise, Equinox considers body fat percentages between 25% and 31% for women, and 18% to 26% for men, as “acceptable.” Women with body fat of 21% to 24%, and men with 14% to 17%, are “fit.” People who reach even lower levels of body fat are considered “athletic,” she says.
The findings of the Mayo study, which was published in November in the European Heart Journal, suggest that reducing heart risk requires increasing the percentage of lean muscle mass at the expense of body fat. That underscores the importance of exercise in maintaining cardiovascular health—including weight lifting and other resistance training, which helps build lean body mass.
Eating a healthy diet is important in reducing body fat, too, but Dr. Lopez-Jimenez observes that if you only restrict calories, you risk losing an equal amount of body fat and lean muscle tissue and thus you could end up weighing less without significantly reducing the percentage of body fat.
Sara Bakken Lee, a 39, a Mayo Clinic staffer, is stepping up her weight training as part of an intense regular exercise program in an effort to get her body fat percentage to 23% from about 26% in December.
When she began to target body fat in her exercise program two years ago, her BMI was 26, just slightly into the overweight category. “I didn’t like being in that category when I didn’t think of myself as being overweight.” Her body fat at the time was 33.7%.
This December, after losing weight on a diet and continuing with a six-day exercise program, her BMI was 23.4, with body fat at 26%. “I’m in the moderately lean category, which makes me very happy.” She hopes to reach a body fat level of 23% by June by adding a third day of weight-lifting to her workout routine.
“If you’re at a sloppy normal weight, that’s not going to be good for you,” says John M. Jakicic director of the physical activity and weight management research center at University of Pittsburgh, who wasn’t involved with the study. “It argues that exercise is the intervention we should be targeting.”
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