Four obese patients were given a single-meal diet (Kcal, 684) for two periods of three days each. CO2 production and 02 consumption were measured every four hours for 30'. At the same times urine samples were collected for nitrogen evaluations. By Consolatio's formulas the amount of carbohydrates, lipids and proteins oxidated in the three days of both periods was calculated. No changes in carbohydrate and lipid oxidation rates were found during the three days with meal at h.10, while a progressive increase in lipid oxidation and a progressive decrease in carbohydrates oxidation could be observed with meal at h. 18. No change with both regimes could be observed in protein oxidation. Furthermore a circadian rhythm of lipid and carbohydrate oxidation with both regimens was observed, while protein oxidation showed a circadian rhythm only with meal at h.10.