Title of article:

Composition of Weight Loss While Dieting: Comparison of Research and Clinically-Based Methods

Authors: Nuñez C, Beyer J, Strain G, Zumoff B, Kovera A, Gallagher D, Heymsfield SB.
Poster presented at: NAASO meeting, Cancun, Mexico, November 1997.

Abstract

Objective: Monitoring composition of weight loss during dieting is an important aspect of evaluating a patient's treatment program. On conventional diets ~75% of weight loss consists of fat (i.e., fat/body weight ~0.75). Research-based methods such as underwater weighing (UWW) and dual energy X-ray absorptiometry (DXA) are useful in assessing composition of weight loss, although not much information is available on accuracy/comparability of clinical methods including anthropometry (Anth) and bioimpedance analysis (BIA). The aim of this study was to compare body composition changes with weight loss between research-based methods and clinical methods.
Design: 16 week weight loss study of healthy obese subjects on prescribed low calorie diet.
Methods: Change in fat mass was assessed with UWW, DXA [Lunar DPX], Anth (Durnin-Womersley), and BIA (Tanita TBF 305).
Results: The table shows the correlation between methods

	Auth	UWW	DXA	BIA
Auth		0.657	0.757	0.745
UWW	0.657		0.822	0.834
DXA	0.757	0.822		0.877
BIA	0.745	0.834	0.887

There were 73 subjects with (X±SD) age 42.6±9.9 yrs & BMI=31.7±3.1 kg/m2. Mean group weight loss was 5.4 kg. A correlation matrix with r values for fat mass is shown in table. Both clinical methods were significantly correlated with UWW and DXA, with BIA r's > than Anth. The fraction of weight loss as fat was established for each method by regression: .79 DXA (R2=.83); .77 BIA (.88); .70 UWW (.69); and .57 Anth (.65).

Results: These results suggest clinical methods, notably BIA, correlate with and provide similar composition of weight loss results to research-based body composition methods.

Comments and Key points

This is quite a simple and useful poster, presented at a scientific meeting, and reproduced on the Tanita Corporation website¹.

It shows that Bio-Electrical Impedence is better than Fat thickness measurements ( anthropometry) for measuring a persons body fat percentage.

Bio-Electrical Impedance is " Bioimpedance analysis " or BIA. BIA has 83 to 88% correlation with the expensive reference methods of Underwater weighing or Dual-photon X-ray Absorptiometry ( DXA ). That's pretty good... as good as the correlation between UWW and DXA at 82%.

The Tanita body fat monitor scales use bio electrical impedence methods. The are used in homes, gyms and in scientific research studies.

 

References

1. http://www.tanita.com/professional/abstracts/abstract_main.html

Review & comments by Steven B. Halls, MD, Last edited 26-May-2008 Copyright.

Back to body fat Scientific articles list.