Environmental Nutrition

Normal weight obesity: it sounds like an oxymoron, but it's not.

It's possible to fall in the normal weight range and still have weight-related health issues. New research points out that it's not enough to look at the bathroom scales or your body mass index (BMI, a measure of one's weight in relation to height) in order to determine the status of your health; levels of body fat also need to be monitored. Normal BMI is 18.5-24.9, overweight is 25-29.9, and obese is over 30 (you can calculate your BMI at: www.nhlbisupport.com/bmi/.) Although BMI can be a helpful tool in evaluating your weight, it has limitations. If you're extremely muscular you may have a "false" high BMI, because it does not account for muscle composition. BMI also does not factor in central obesity (weight carried around the abdomen), which has been linked with increased disease risk.

What is normal weight obesity?

This condition is characterized by having a normal BMI with a large percentage of body fat -- more than 30 percent for women and 20 percent for men, according to Mayo Clinic researchers who presented their findings at the American College of Cardiology's Annual Scientific Session in Chicago in 2008. The researchers observed 2,127 normal weight adults (equally divided between men and women) and found that over half of them had normal weight obesity (NWO.) In fact, NWO is so prevalent that Francisco Lopez-Jimenez, M.D., the Mayo Clinic cardiologist leading the study team, estimates that up to 30 million Americans have this condition.

The lowdown on NOW

So what's all the fuss about having a normal weight but a higher body fat percentage? Unfortunately, this condition carries risks similar to being overweight or obese. "In normal weight obesity, people have little of the good things, such as muscle mass and dense bones. In fact, elderly people that are normal weight are likely to have NWO, as they have lower muscle mass and lighter bones," explains Lopez-Jimenez. The Mayo Clinic study revealed that people with NWO are more likely to have metabolic syndrome, which is a cluster of abnormalities that serve as a precursor to diabetes and cardiovascular disease, including elevated blood pressure, blood glucose and triglycerides, and low HDL ("good") cholesterol levels. In another study published in the January 2007 issue of American Journal of Clinical Nutrition, researchers found that NWO women had higher biomarkers of inflammation, putting them at risk for early inflammation, cardiovascular disease and metabolic syndrome.

Should you worry over being "skinny-fat"?

"It's not necessary for everybody to measure their body fat to see if they have NWO," says Lopez-Jimenez. "If someone is very skinny, below a BMI of 18.5, they don't need to check body fat because it is likely very low. If someone is overweight -- over 30-35 BMI, then we know that they already have high body fat. It's in the intermediate range -- when you fall in the normal or mildly elevated BMI -- that you should determine if you're body fat is too high."

While figuring out your body fat percentage isn't as easy as stepping on a scale, there are a number of methods for measuring it. However, Lopez-Jimenez warns that some options are "very accurate but impractical, and some are very simple but useless." He suggests two methods for measuring body fat composition that are both reliable and practical: bioelectric impedance (bioimpedence) and the Bod Pod (air displacement). Bioimpedence, which uses an electrical current to measure body composition levels, has become more popular at fitness centers and clinics because of its ease and relative low cost. But Lopez-Jimenez cautions against falling for home versions of bioimpedence machines sold in drug stores, because they are not very accurate. The Bod Pod, a machine that looks like a plastic space capsule, uses air to displace body volume in order to assess body composition. Available in many locations, such as hospitals and fitness centers, the Bod Pod is very reliable and easy to use.

A truly healthy weight

So how do you focus on getting a healthy body composition beyond the bathroom scales?

While it's important to eat a balanced, healthy diet, this issue is mostly about exercise. Lopez-Jimenez says, "This is more than just about losing weight. If you're at normal weight and you lose more weight, you may not be changing your body fat percentage. You could be losing muscle, not fat. You need to do a combination of aerobic exercise and strength or resistance training exercise."

 

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