Being able to accurately assess body fat levels is an important tool for health care professionals as well as trainers and coaches in the sporting arena. Methods have therefore been created that are able to measure levels of body fat. Underwater weighing is seen as the traditional gold standard, but newer technologies include air displacement plethysmography (ADP) and dual-energy X-ray absorptiometry (DXA). However, use of these methods is confined to research, because of the expense and expertise involved in their use. Because of this, many methods of estimating body fat are substituted in their place in clinical practice. Bioelectrical impedance analysis (BIA) is one method that estimates an individuals body weight based on the electrical resistance to flow through body tissues. It is relatively cheap and widely used in sport and the health industry.
Research has investigated the estimates of body fat attained by BIA and compared them with the methods of measuring body fat. For example, researchers1 determined the effects of sex and adiposity on the percentage body fat attained by measuring with DXA or estimating with BIA. The results showed that the correlations between the two methods was closer for women than for men. In addition, BIA tended to predict a lower mean percentage body fat when compared to measurements by DXA. However, BIA overestimated percentage body fat in men and women by 3.03 % and 4.40 % when body fat was < 15 % in men and < 25 % in women, but underestimate percentage body fat by 4.32 % and 2.71 % when percentage body fat was > 15 % in men and > 25 % in women.
These results would suggests that BIA is a cost effective alternative way to estimate body fat percentage when compared to measurements by DXA. The results of this study support previous findings that have shown over- and under-estimates in the use of BIA in various population types. The fact that BIA tends to overestimate body fat in lean subjects but underestimate body fat in obese subjects can be taken into consideration when making the analysis. As well as cost, the main advantages of BIA are that is requires little training to use and an analysis can be performed in minutes. In a clinical or sport setting, it is often changes in body fat rather than the actual amount that is of interest, and if this is the case then BIA remains a valid method of estimation as long as the operator is aware of the under- and over-estimation.
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