By David Blyweiss, M.D.

Normal weight obesity: it sounds like an oxymoron, but it’s not. Even if you look like you fall within a normal weight range, you can still have weight-related health issues. Surprised? Most people are. But new research points out that it’s not enough to look at the bathroom scales or your body mass index (BMI) 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 doesn’t 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 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. 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. In fact, the condition is so prevalent, that the Mayo Clinic cardiologist leading the study team estimates that up to 30 million Americans have this condition.

Normal weight obesity carries risks similar to being overweight or obese, specifically a low muscle mass and less bone density. The Mayo Clinic study revealed that people with normal weight obesity are also more likely to have metabolic syndrome, which is a cluster of health issues like high blood pressure, blood sugar and triglycerides and low HDL (good) cholesterol that are a precursor to diabetes and cardiovascular disease. Another study in the American Journal of Clinical Nutrition found that women with normal weight obesity had higher biomarkers of inflammation, which also put them at risk for cardiovascular disease and metabolic syndrome.

Are you “skinny-fat”?  Even if you have a normal BMI, you could be. Fortunately, you can adopt some healthful habits that can help you achieve a healthy body composition.

Eating a whole foods diet filled with fresh fruits and vegetables is a good first step. It’s also crtical to avoid processed foods, refined sugar and trans fats. But as important as a healthy diet is, preventing normal weight obesity is mostly about exercise. After all, if you are at a normal weight and you lose more weight, you may not be changing your body fat percentage. You could be losing muscle, not fat.

To preserve muscle while reducing fat, you need to do a combination of aerobic exercise and strength or resistance training exercise. I recommend getting at least 30 minutes of moderate-intensity aerobic exercise every day (one hour is even better). It’s also important to participate in some form of muscle-strengthening activity that involves all the major muscle groups at least two days per week.

Supplements can also support the formation of lean muscle while helping the body burn fat. Among my favorites are the amino acids L-carnitine and L-arginine. Studies show that supplemental carnitine reduces fat, increases muscle mass, and reduces fatigue. And, according to a recent study published in the Journal of Nutrition, L-arginine supplementation promotes muscle over fat gain and may provide a useful treatment for improving the metabolic profile and reducing body fat. Combining these two amino acids with healthy lifestyle strategies can help you be as healthy on the inside as you look on the outside.

References:

De Lorenzo A. Normal-weight obese syndrome: early inflammation?American Journal of Clinical Nutrition. 2007; 85:40-45.

Jobgen W. Dietary L-Arginine Supplementation Reduces White Fat Gain and Enhances Skeletal Muscle and Brown Fat Masses in Diet-Induced Obese Rats. Journal of Nutrition. 2009; 139: 230-237.

Romero-Corral A. Normal weight obesity: a risk factor for cardiometabolic dysregulation and cardiovascular mortality. European Heart Journal. 2010;31:737-746