COMPARISON OF METHODS OF ESTIMATING BODY COMPOSITION CHANGES DURING WEIGHT LOSS IN WOMEN

Authors: Siders, William; Lukaski, Henry

Submitted to: North Dakota Academy of Science Proceedings
Publication Type: Other
Publication Acceptance Date: 9/15/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Little information exists about the ability of common body composition (fat, muscle, water, bone) assessment methods to document changes during weight loss. Over-fat women, participating in a controlled weight loss program of reduced food intake and increased exercise, were studied before and during weight loss. As body weight decreased, body fat also decreased. Dual x-ray absorptiometry measured greater fat loss than skinfold thickness measurements, which yielded greater losses of muscle than the x-ray method. The amount of nitrogen lost (an indicator of muscle loss) during weight loss did not exceed dietary nitrogen intake. These findings indicate that muscle mass can be preserved when weight loss is accomplished with a combination of moderate food restriction and exercise. Also, the dual x-ray method is a valid, and probably preferred, technique to monitor body composition change. This information will be useful to medical personnel involved in obesity research and people who desire to lose weight.

Technical Abstract: Thirty women, aged 21 to 39 years, were studied during a weight stabilization period and for an additional 120 days of caloric restriction and increasing exercise. Body composition was assessed monthly by using anthropometry, two forms of hydrodensitometry and dual x-ray absorptiometry. As body weight decreased, all of the methods showed decreases in fat weight but assessments by dual x-ray absorptiometry decreased more than those by anthropometry. Also, only assessments of fat-free weight from anthropometry decreased significantly during weight loss. Nitrogen balance, an independent measure of body composition, did not change during weight loss. These findings demonstrate that fat-free weight is maintained when weight loss includes a progressive exercise program, and that dual x-ray absorptiometry is a valid and preferred method of determining change in body composition during weight loss.