A large increase in the breakdown of body protein during the initial stages of starvation
provides the liver and kidney with the amino acids alanine and glutamine to make glucose.
However, there is a gradual decrease in protein breakdown which occurs in concert with the
decreasing glucose requirements.
Although the exact mechanisms behind the ‘protein sparing’ effect of ketosis are not
entirely established, there are at least four possible mechanisms by which ketogenic diets may
spare protein. These include decreased glucose requirements, decreased excretion of ketones
from the kidneys, a possible direct effect of ketones on protein synthesis, and the drop in thyroid
levels seen during starvation.
References Cited
- Fery F et. al. Hormonal and metabolic changes induced by an isocaloric isoprotienic ketogenic
diet in healthy subjects. Diabete Metab (1982) 8: 299-305. - Bloom W and Azar G. Similarities of carbohydrate deficiency and fasting. Part I: weight loss,
electrolyte excretion and fatigue. Arch Intern Med (1963) 112: 333-337. - Azar G and Bloom W. Similarities of carbohydrate deficiency and fasting. Part II: Ketones,
nonesterified fatty acids and nitrogen excretion. Arch Intern Med (1963) 112: 338-343. - Cahill G. Starvation. Trans Am Clin Climatol Assoc (1982) 94: 1-21.
- Cahill G. Starvation in man. N Engl J Med (1970) 282: 668-675
- Cahill G and Aoki TT. How metabolism affects clinical problems Medical Times (1970)
98: 106-122. - Cahill, G et. al. Hormone-fuel relationships during fasting. J Clin Invest (1966) 45: 1751-1769
- Owen OE et. al. Liver and kidney metabolism during prolonged starvation. J Clin Invest (1969)
48: 574-583 - Owen OE et. al. Protein, fat and carbohydrate requirements during starvation: anaplerosis
and cataplerosis. Am J Clin Nutr (1998) 68: 12-34. - Wolfe RR et. al. Effect of short-term fasting on lipolytic responsiveness in normal and obese
human subjects. Am J Physiol (1987) 252: E189-E196 - Jensen MD et. al. Lipolysis during fasting: decreases suppression by insulin and decreased
stimulation by epinephrine. J Clin Invest (1987) 79: 207-213. - Haymond MW et. al. Effects of ketosis on glucose flux in children and adults. Am J Physiol
(1983) 245: E373-E378 - Garber AJ et. al. Hepatic ketogenesis and gluconeogenesis in humans. J Clin Invest (1974)
54: 981-989. - Carlson MG et al. Fuel and energy metabolism in fasting humans. Am J Clin Nutr. (1994)
60: 29-36. - Robinson AM and Williamson DH Physiological roles of ketone bodies as substrates and
signals in mammalian tissues. Physiol Rev (1980) 60: 143-187. - Phinney S.D. et. al. The human metabolic response to chronic ketosis without caloric
restriction: physical and biochemical adaptations. Metabolism (1983) 32: 757-768. - Swendseid ME et. al. Plasma amino acid levels in subjects fed isonitrogenous diets containing
different proportions of fat and carbohydrate. Am J Clin Nutr (1967) 20: 52-55. - Felig P. et. al. Amino acid metabolism during prolonged starvation. J Clin Invest (1969)
48: 584-594.