Resting metabolic requirements of men and women

The resting metabolic rates (RMRs) of 44 lean and obese women, 8 of whom were trained athletes, and of 60 lean and obese men were measured by indirect calorimetry. These healthy humans, ranging from 18 to 82 years old and from 43 to 171 kg in weight, were mentally and physically active. Body composition was determined by densitometry and skinfold thickness. Stepwise multiple regression analysis was used to determine whether one or several variables best predicted RMR. Body compositional variables reflecting active protoplasmic tissue were all highly interrelated. Body weight alone yielded prediction values for RMR comparable to those of other variables of active protoplasmic tissue mass. Among these mentally and physically active women and men, the influence of age on RMR was trivial, and regional distribution of fat had no influence on the RMR. The 95% confidence limits for RMR in both lean and obese subjects were broad. Thus, metabolic efficiency is not necessarily or exclusively related to obesity. In fact, the caloric requirements of humans, based on body weight or active protoplasmic tissue mass, may vary twofold. With the exception of the elderly men, the classic prediction equations and tables developed during the first half of this century greatly overestimated the RMR of healthy lean and obese humans. Therefore, new regression equations for predicting the RMR based on weight and fat-free mass were developed.