Progressive alterations in lipid and glucose metabolism during short-term fasting in young adult men

Am J Physiol. 1993 Nov;265(5 Pt 1):E801-6. doi: 10.1152/ajpendo.1993.265.5.E801.

Abstract

Stable isotope tracers and indirect calorimetry were used to evaluate the progressive alterations in lipid and glucose metabolism after 12, 18, 24, 30, 42, 54, and 72 h of fasting in six healthy male volunteers. The rates of appearance (Ra) of glycerol and palmitic acid in plasma doubled from 2.08 +/- 0.22 and 1.63 +/- 0.20 mumol.kg-1 x min-1, respectively, after 12 h to 4.36 +/- 0.36 and 3.26 +/- 0.40 mumol.kg-1 x min-1, respectively, after 72 h of fasting (P < 0.01). Of the total increase in lipid kinetics, 60% occurred between 12 and 24 h of fasting; the greatest interval change occurred between 18 and 24 h of fasting. Glucose Ra and plasma concentration decreased by approximately 25% between 12 h (11.0 +/- 0.4 mumol.kg-1 x min-1 and 5.58 +/- 0.08 mmol/l, respectively) and 72 h (8.3 +/- 0.3 mumol.kg-1 x min-1 and 4.14 +/- 0.10 mmol/l, respectively) of fasting (P < 0.01), but no statistically significant changes occurred between 18 and 24 h of fasting. Plasma insulin decreased by approximately 50% between 12 h (64.6 +/- 12.9 pmol/l) and 72 h (30.1 +/- 7.9 pmol/l) of fasting (P < 0.001). Of the total decline in plasma insulin, 70% occurred within the first 24 h of fasting. These results demonstrate that the mobilization of adipose tissue triglycerides increases markedly between 18 and 24 h of fasting in young adult men. The early alterations in lipid metabolism are associated with a decline in circulating insulin but do not seem to be regulated by changes in glucose kinetics or plasma glucose concentrations.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adult
  • Blood Glucose / metabolism*
  • Deuterium
  • Energy Metabolism*
  • Fasting / physiology*
  • Fatty Acids, Nonesterified / blood*
  • Glucose / metabolism
  • Glycerol / blood*
  • Humans
  • Isotope Labeling / methods
  • Lipolysis
  • Male
  • Palmitic Acid
  • Palmitic Acids / blood*
  • Regression Analysis
  • Time Factors
  • Triglycerides / metabolism

Substances

  • Blood Glucose
  • Fatty Acids, Nonesterified
  • Palmitic Acids
  • Triglycerides
  • Palmitic Acid
  • Deuterium
  • Glucose
  • Glycerol