Body composition changes during a period of weight loss
The rapidly increasing prevalence of obesity has attracted the attention of the World Health Organization, which has issued a statement on the matter. Obesity is related to a number of disease states including hypertension, hypercholesterolemia, and diabetes. Body fat is also associated with increased mortality. Weight loss reduces cardiovascular disease risk and improves insulin sensitivity. Weight loss practices and techniques with an emphasis on fat loss have become widespread, and the need for accurate measurements for the assessment of body composition is important. There are a number of methods to assess body composition. While some are more accurate than others, the cost of more accurate methods is not always feasible. Therefore, it is important to assess the validity of less expensive techniques. There is little research comparing body composition methods over a period of weight loss. The purpose of this study was to assess body composition by three different methods, DXA, bioelectrical impedance analysis (BIA), and ADP, before and after a 6-month weight loss program. The researchers used both conventional bioelectrical impedance machines as well as the Tanita body fat analyzer.
Fifty-six healthy but overweight participants, 34 women and 22 men (age, 52 [+ or -] 8.6 years; weight, 92.2 [+ or -] 11.6 kg; body mass inside (BMI), 33.3 [+ or -] 2.9 kg/[m.sup.2]) were studied in an outpatient setting before and after 6 months of weight loss (weight loss, 5.6 [+ or -] 5.5 kg). Subjects were excluded if they had initiated a new drug therapy within 30 days of randomization, were in a weight loss program, or took a weight loss drug within 90 days of randomization. Subjects were randomly assigned either to a self-help program, consisting of two 20-minute sessions with a nutritionist and provision of printed materials and other self-help resources, or to attendance at meetings of a commercial program (Weight Watchers). Body composition was examined by each of the methods before and after weight loss.
BIA (42.4 [+ or -] 5.8%) underestimated percentage fat, whereas the BodPod overestimated percentage fat compared with DXA (46.1 [+ or -] 7.9%) before weight loss. Tanita and tetrapolar BIA overestimated FFM before weight loss, whereas BodPod underestimated FFM. Both BIA and ADP are accurate compared with DXA when assessing body composition. However, these results, along with previous studies including athletes and leaner individuals, indicate that these methods may be less reliable with increasing body fat, which may have to do with hydration status. Overall, the correlation coefficients between each of the methods for body composition compared with DXA were high. In addition, each of the methods was sensitive enough to detect changes with weight loss. Brozek was slightly more accurate in predicting changes with weight loss compared with Siri. BIA using the hand/foot method was also more accurate than the Tanita scale method. However, it would not be beneficial to use these methods interchangeably to detect body compositional changes over weight loss.
M. Frisard, F. Greenway, J. DeLany, Comparison of Methods to Assess Body Composition Changes during a Period of Weight Loss. Obes Res; 13:845-854 (May, 2005). [Correspondence: James P DeLany, 6400 Perkins Road, Baton Rouge, LA 70810.