Nutrition Bytes

High fat diets seem to improve exercise endurance in animals, although this effect is not uniformly found in humans. Enhancements in endurance appear to be due to physiological changes in skeletal muscles and their milieu, including increased fat oxidative capacity, increased plasma free fatty acid levels, greater mitochondrial density, and increased activities of b -hydroxy-acyl-CoA-dehydrogenase (b -HAD) and citrate synthase. Glycogen may also be spared by posttransformation regulation of glycogen phosphorylase. High fat diets may have a more powerful effect in animals because the diets in animal experiments were typically more extreme than those given to humans.