AJP - Endocrinology and Metabolism, Vol 245, Issue 4 318-E325, Copyright © 1983 by American Physiological Society
Ketone body turnover during and after exercise in overnight-fasted and starved humans
F. Fery and E. O. Balasse
The concentration of ketone bodies and their rate of transport (estimated
with an infusion of beta-[14C]-hydroxybutyrate) were determined before,
during, and after exercise in overnight-fasted and 3- to 5-day-fasted
subjects who walked on a treadmill for 2 h at approximately 50% of their
VO2max. In overnight-fasted subjects, exercise increased the rate of
turnover (+125% after 2 h) and the metabolic clearance rate of ketone
bodies whose concentration rose from 0.20 to 0.39 mM. Discontinuation of
exercise was associated with a marked increase in ketone levels (+0.73 mM
after 30 min of recovery) that was related to a further stimulation of
ketogenesis (+19%) and to a marked drop of the metabolic clearance rate to
below preexercise values. In sharp contrast with overnight-fasted subjects,
starved subjects (with a resting ketone level averaging 5.7 mM) responded
to work by a decrease in the turnover rate and in the concentration of
ketones, their metabolic clearance rate remaining unchanged. Thus, the
response of ketogenesis and muscular ketone uptake to exercise are both
markedly influenced by the initial degree of fasting ketosis.
