Childhood and adult obesity is an epidemic in the USA. It is important to have valid and reliable tools to assess growth and body composition. It is essential that we develop safe and accurate tools to assess body composition as well as readily affordable. Devices that accurately depict body fat percentage (%BF) can be used as a tool to evaluate an individual’s weight loss or gain over a period of time. Body composition analysis is important for understanding prortional changes in fat and lean mass for healthy individuals well as individuals with various health conditions. A number of devices are available on the market. and ales of economical body composition analysers (i.e. bioe_~ trical impedance devices). Traditionally, assessing body composition relied upon the principle of underwater weighing, which is the gold standard. Technology has improved and various new methods are available measure body composition. Dual-energy X-ray absorptiometry (DEXA) has become the preferred method for measuring body composition. Jensky-Squires and colleagues tested the validity and reliability of the BioSpace InBody 320, Omron and Bod-eComm body composition devices in men and women ( 21-80 years) and boys and girls ( 10-17 years). They analysed percentage body fat (%BF) and compared the results with dual-energy X-ray absorptiometry (DEXA) in adults and compared the results of the InBody with underwater weighing (UW) in children. All body composition devices were correlated to DEXA except the Bod-eComm in women aged 71-80 years . In girls, the lnBody %BF was correlated with UW (r 0·79; P:S;0·010); however, a more moderate correlation (r 0·69; P:s;O·01O) existed in boys. Bland-Altman plots indicated that all body composition devices underestimated %BF in adults (1·0-4·8 %) and overestimated %BF in children (0·3-2·3 %). Independent t tests showed that the mean %BF assessed by the Bod-eComm in women (aged 51 -60 and 71-80 years) and in the Omron (age 18-35 years) were significantly different compared with DEXA. In men, the Omron (aged 18-35 years), and the lnBody (aged 36-50 years) were significantly different compared with DEXA (P=0·025; P=0·040 res pectively). In addition, independent t tests indicated that the InBody mean %BF in girls aged 10-17 years was significantly different from UW. Pearsori’s correlation analyses demonstrated that the Bod-eComm (men and women) and Omron (women) had significant mean differences compared with the reference criterion. Therefore, the %BF output from these two devices should be interpreted with caution. The interesting point that might be explored is are they all measuring the same thing?