The present invention relates to dietary compositions comprising reduced level of methionine, tryptophan, all amino acids, or protein, dietary compositions comprising glycerol as a substitute for monosaccharides, disaccharides, and polysaccharides, and hypocaloric or calorie free diets with reduced level of energy, carbohydrates, or protein. Also disclosed are methods of using these compositions and diets, as well as fasting, to protect subjects against chemotherapy, radiotherapy, oxidative stress, or aging.
