Similarity of obesity indices in clinical studies of obese adults: a factor analytic study

The similarity of measurements obtained with six commonly used obesity indices was assessed with correlational and factor analyses performed on data for 951 obese adults participating in a weight reduction study. Intercorrelations among the indices were found to be very high, with a mean of 0.96. A factor analysis of the six indices resulted in a single factor which accounts for 97% of the aggregate variance in the six indices. A factor analysis of the six indices plus height and weight resulted in two factors. The six indices loaded nearly perfectly on one factor and not at all on the second. Height loaded perfectly on the second factor. The results of these analyses constitute strong empirical evidence that the obesity indices are measuring the same thing and that factor is independent of height. Although anthropological or other special studies may necessitate the use of a particular index, these results suggest that it should make little difference which of the six indices is used in a clinical study of obesity with obese adults.