Search tips
Search criteria 


Logo of jcinvestThe Journal of Clinical Investigation
J Clin Invest. 1980 November; 66(5): 1152–1161.
PMCID: PMC371554

Capacity for Moderate Exercise in Obese Subjects after Adaptation to a Hypocaloric, Ketogenic Diet


To study the capacity for moderate endurance exercise and change in metabolic fuel utilization during adaptation to a ketogenic diet, six moderately obese, untrained subjects were fed a eucaloric, balanced diet (base line) for 2 wk, followed by 6 wk of a protein-supplemented fast (PSF), which provided 1.2 g of protein/kg ideal body wt, supplemented with minerals and vitamins. The mean weight loss was 10.6 kg.

The duration of treadmill exercise to subjective exhaustion was 80% of base line after 1 wk of the PSF, but increased to 155% after 6 wk. Despite adjusting up to base line, with a backpack, the subjects' exercise weight after 6 wk of dieting, the final exercise test was performed at a mean of 60% of maximum aerobic capacity, whereas the base-line level was 76%. Resting vastus lateralis glycogen content fell to 57% of base line after 1 wk of the PSF, but rose to 69% after 6 wk, at which time no decrement in muscle glycogen was measured after >4 h of uphill walking. The respiratory quotient (RQ) during steady-state exercise was 0.76 during base line, and fell progressively to 0.66 after 6 wk of the PSF. Blood glucose was well maintained during exercise in ketosis. The sum of acetoacetate and beta hydroxybutyrate rose from 3.28 to 5.03 mM during exercise after 6 wk of the PSF, explaining in part the low exercise RQ.

The low RQ and the fact that blood glucose and muscle glycogen were maintained during exhausting exercise after 6 wk of a PSF suggest that prolonged ketosis results in an adaptation, after which lipid becomes the major metabolic fuel, and net carbohydrate utilization is markedly reduced during moderate but ultimately exhausting exercise.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.6M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • Bergström J, Hultman E. A study of the glycogen metabolism during exercise in man. Scand J Clin Lab Invest. 1967;19(3):218–228. [PubMed]
  • Hultman E. Studies on muscle metabolism of glycogen and active phosphate in man with special reference to exercise and diet. Scand J Clin Lab Invest Suppl. 1967;94:1–63. [PubMed]
  • Horton ES, Johnson C, Lebovitz HE. Carbohydrate metabolism in uremia. Ann Intern Med. 1968 Jan;68(1):63–74. [PubMed]
  • O'Connell M, Robbins DC, Horton ES, Sims EA, Danforth E., Jr Changes in serum concentrations of 3,3',5'-triiodothyronine and 3,5,3'-triiodothyronine during prolonged moderate exercise. J Clin Endocrinol Metab. 1979 Aug;49(2):242–246. [PubMed]
  • Krogh A, Lindhard J. The Relative Value of Fat and Carbohydrate as Sources of Muscular Energy: With Appendices on the Correlation between Standard Metabolism and the Respiratory Quotient during Rest and Work. Biochem J. 1920 Jul;14(3-4):290–363. [PubMed]
  • Owen OE, Reichard GA., Jr Human forearm metabolism during progressive starvation. J Clin Invest. 1971 Jul;50(7):1536–1545. [PMC free article] [PubMed]
  • Hagenfeldt L, Wahren J. Human forearm muscle metabolism during exercise. VI. Substrate utilization in prolonged fasting. Scand J Clin Lab Invest. 1971 Jun;27(4):299–306. [PubMed]
  • Costill DL, Sparks K, Gregor R, Turner C. Muscle glycogen utilization during exhaustive running. J Appl Physiol. 1971 Sep;31(3):353–356. [PubMed]
  • Costill DL, Jansson E, Gollnick PD, Saltin B. Glycogen utilization in leg muscles of men during level and uphill running. Acta Physiol Scand. 1974 Aug;91(4):475–481. [PubMed]
  • Drenick EJ, Fisler JS, Johnson DG, McGhee G. The effect of exercise on substrates and hormones during prolonged fasting. Int J Obes. 1977;1(1):49–61. [PubMed]
  • Blackburn GL, Flatt JP, Clowes GH, Jr, O'Donnell TF, Hensle TE. Protein sparing therapy during periods of starvation with sepsis of trauma. Ann Surg. 1973 May;177(5):588–594. [PubMed]
  • Apfelbaum M. The effects of very restrictive high protein diets. Clin Endocrinol Metab. 1976 Jul;5(2):417–430. [PubMed]
  • Genuth SM, Castro JH, Vertes V. Weight reduction in obesity by outpatient semistarvation. JAMA. 1974 Nov 18;230(7):987–991. [PubMed]
  • Sigler MH. The mechanism of the natriuresis of fasting. J Clin Invest. 1975 Feb;55(2):377–387. [PMC free article] [PubMed]
  • Spark RF, Arky RA, Boulter PR, Saudek CD, O'Brian JT. Renin, aldosterone and glucagon in the natriuresis of fasting. N Engl J Med. 1975 Jun 19;292(25):1335–1340. [PubMed]
  • Kolanowski J, Salvador G, Desmecht P, Henquin JC, Crabbé J. Influence of glucagon on natriuresis and glucose-induced sodium retention in the fasting obese subject. Eur J Clin Invest. 1977 Jun;7(3):167–175. [PubMed]

Articles from The Journal of Clinical Investigation are provided here courtesy of American Society for Clinical Investigation