Growth and Fat Deposition in the Mouse

A Definition of Obesity

¹ From the Department of Biology, Brown University, Providence, Rhode Island

Mice of the C₅₇BL/Fn strain and the I/Fn strain were placed after weaning on a diet containing 50% fat. The carcass fat content of C₅₇BL/Fn mice increased linearly with the age of the animals. Plotting fat content against fat-free weight for young animals of the C₅₇BL/Fn and all animals of the I/Fn strains yielded a straight line of slope 0.1. The data for older C₅₇ animals (3–5 months) did not fall on this line. Obesity is defined in terms of the regression of fat content on fat-free weight.