The amount of protein in the diet modulates both total food intake and body weight gain. Many investigators have studied the relationship between dietary protein and food intake and weight gain, but most studies have ignored the effect of age. Toyomizu and coworkers* noted a prior study that quantitatively related growth and food intake to dietary protein including the effect of age. The equations used to quantify these effects contain several parameters, including one relating to the food intake at maturity F and one relating to the body weight at maturity W. It was concluded that these two parameters were independent of the amount of dietary protein. However, Toyomizu and colleagues thought that the range of dietary proteins studied was too limited (14–36 percent of energy intake), and, therefore, they studied the growth and food intake of rats fed a much broader range of diets such that the fraction of protein in the diet P ranged from 5 to 80 percent of the gross energy available in the diet. Is W independent of dietary protein (the data are in Table D-47, Appendix D)? Toyomizu and coworkers used the equation .