In a previous communication,1were reported the results of studies of nitrogen excretion in obese patients on diets low in calories, containing varying amounts of protein. It was noted that a negative nitrogen balance was unusual in patients on diets containing 90 Gm. of protein, and that the loss of nitrogen on an intake of from 13 to 14 Gm. of protein was not significant. The general conclusion reached was that the fat constitutes a mobile supply of energy which is so easily requisitioned that starvation sequelae do not develop, provided carbohydrate is furnished for antiketogenesis and protein for the "wear and tear quota." In this paper a study of the effect of such diets on the rate of loss in weight and on the metabolic rate is reported. The periods of observation were sufficient to obviate minor variations in weight due to water retention, and thus to establish