If you're burning calories and lifting weights, you could actually be losing inches of fat and adding muscle mass - even if your scale is telling you your weight has remained the same or increased. Some people have turned to body fat measurement (also known as body composition testing) instead of the scale to measure their fitness progress. But determining the most accurate method of body fat measurement can be difficult, so a recent study published in the journal Medicine & Science in Sports & Exercise compared two popular methods of measuring body composition in people who were losing weight.

Twelve overweight women and ten men participated in a weight-loss study. During an 8-week weight-loss program that restricted calories and encouraged exercise, the participants had their body fat percentages measured using dual-energy x-ray absorptiometry (also known as DXA) and air displacement plethysmography (also known as ADP or the Bod Pod). DXA uses X-rays to measure body fat, muscle, and bone mineral. During the scan, a person must lie still on his or her back for about 10 minutes while a computer produces an image of body tissues and a body fat percentage. If you have your body fat percentage measured with the Bod Pod, you'll sit in a chamber for about 5 minutes, and the air that your body displaces will be measured.

There were few differences in body fat percentage measurements between the DXA and ADP methods. Researchers concluded that people who were on a weight-loss program would receive similar body fat percentage results from either a DXA or ADP test.

There are many methods for measuring body fat, and some are more effective than others. Talk to your health care professional about having your body fat percentage measured; qualified testers are often available at fitness centers, community centers or gyms.

Related information Evaluating your weight

Sources:  Weyers AM, Mazzetti SA, Love DM, Gómez AL, Kraemer WJ, Volek JS. Comparison of methods for assessing body composition changes during weight loss. Med. Sci. Sports Exerc., March 2002, Vol. 34, No. 3, p. 497–502.