Summary ·1. Under the conditions öf pair feeding, water-deprived rats predominantly use fat äs a metabolic fuel, whereas total energy turnover äs measured by oxygen consumption is not altered. t.2. Plasma free fatty acids are elevated in dehydrated rats, indicating enhanced lipolysis.. 3. Reduced hepatic fatty acid synthesis and reduced triacylglycerol secretion into the blood seem to be the main factors for the decfease of plasma triacylglycerol, observed 48 hours after the onset of water j deprivation.4. Enhanced plasma levels of corticosterone (about 100%) and glucagon (about 50%) may contribute to the ; metabolic Situation observed in water deprivation.