Waist Size Matters, Fit or Not

Q: I'm in the armed forces and required to pass a physical fitness test every year that includes timed pushups and sit-ups, a mile and a half run, and measurements for body mass index and waist circumference. Many of my colleagues believe that if a person is fit, their waist size should not matter. Is this really a necessary part of a fitness assessment?

A:  Your assessments are rating you not just on your fitness level, but on your health status, too.

Standardized fitness tests like pushups and the timed 1.5-mile run are used to indicate the status of your cardiovascular and muscular endurance.

But BMI and waist measurements are not evaluating your physical fitness. They're assessing your health risks.

The BMI is the starting point; it reflects your relative weight for your height and is generally associated with body-fat percentage. The average person with a BMI of 25 or above is considered overweight because, at this BMI, health risks increase for conditions such as high blood pressure and high cholesterol and/or glucose intolerance.

However, fit people aren't necessarily at risk of poor health simply because they have a slightly higher BMI. Since a trained exerciser tends to have more lean body mass, he or she can be heavier than normal, but also leaner than normal.

So an above-normal BMI is not necessarily a reflection of the risks associated with being overly fat—unless a person has excess fat in their abdominal area. Ab fat is associated with increased risks of morbidity and diseases like cardiovascular disease and diabetes. Generally, a person with an "overweight" BMI who has a waist circumference that is greater than 35 inches for women or greater than 40 inches for men is considered to be a candidate for weight-loss treatment to prevent more weight gain that could lead to obesity, and to produce modest weight loss.

Although the best way to gauge the amount of excess visceral fat is with high-tech equipment such as CT scans and MRIs, these methods are pricey and impractical. So waist circumference is used as a measure of whether excess fat in the abdomen is out of proportion with a person's total body fat, according to National Institute of Health’s Clinical Guidelines on the Identification, Evaluation and Treatment of Overweight and Obesity in Adults.

So that's the likely reason your fitness test includes waist size.

Of course, the health benefits that come with being highly fit may actually trump the health risks a bigger belly poses. In fact, researchers at The Cooper Institute in Dallas found that being fit and fat is healthier for men and women than being unfit and thin.

But you can also be fit and unhealthy, or fit in ways that aren't necessarily helping your health all that much. For example, if you are in great shape but eat poorly and drink too much alcohol, you may be able to win a race and lift a heavy log—but you could still have atherosclerotic plaque in your blood vessels. Or, if you are strong but not cardiovascularly fit—you do well in the pushup and sit-up portion of the test, but only average in the timed run—and you have extra flab in your gut, your fitness is not the type that can provide you with the most protection against certain health conditions.

Being fit is key for all-around health—and having less abdominal fat is healthier.

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Martica is a Manhattan-based exercise physiologist and nutritionist and an award-winning fitness instructor. She has written for a variety of publications including Self , Health , Prevention , The New York Times and others. Martica is the author of seven books, including her latest, - Cross-Training for Dummies . (Read her full bio.)