A factor analytic--genetic approach to the relation between obesity and behavior in mice

Genetically heterogenous mice (N = 377) were reared on either high- or low-fat diets for the first 40 days of life. The mice were cross fostered to permit the separation of genetic and environmental effects in a sibling analysis. A total of 26 measures were taken on these mice, including oxygen consumption, activity, sucrose consumption, body weight changes when bitter or high-fat diets were given as the only food, and various morphological measures. A principal-factor analysis of these measures produced eight factors, most of which appeared to be "instrument" factors rather than general factors. Analyses of variance on the factor scores indicated that genetic influences contributed to five of the factors and sex contributed to three of the factors. However, none of the main effects of diet, gene by environment interactions, or sex by environment interactions were significant. Although obesity and behaviors were correlated, the magnitudes of the correlations were generally small.