Computation of the effective body mass for metabolic studies of lean and obese rats

The whole-animal metabolic rates of lean and obese rats cannot be directly compared because obese rats have much greater body mass than lean rats. Expressing the results as metabolic rate per unit of body mass is also not satisfactory because lean and obese rats of the same size have different body compositions. To make possible comparisons between the two types of rats, metabolic rate must be expressed per unit of effective body mass. Effective body mass for lean and obese Zucker rats can be calculated as 1.00 M0.75 and 0.82 M0.75, respectively, where M is the mass of the animal.