Skip to main page content
Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 1980 Nov;66(5):1152-61.
doi: 10.1172/JCI109945.

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

Free PMC article

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

S D Phinney et al. J Clin Invest. .
Free PMC article

Abstract

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.

Similar articles

See all similar articles

Cited by 24 articles

See all "Cited by" articles

References

    1. Biochem J. 1920 Jul;14(3-4):290-363 - PubMed
    1. J Clin Endocrinol Metab. 1979 Aug;49(2):242-6 - PubMed
    1. Scand J Clin Lab Invest. 1971 Jun;27(4):299-306 - PubMed
    1. Scand J Clin Lab Invest. 1967;19(3):218-28 - PubMed
    1. JAMA. 1974 Nov 18;230(7):987-91 - PubMed

Publication types

Feedback