SERUM FREE FATTY ACID CONCENTRATION DURING POST-EXERCISE RECOVERY (INSULIN, HUNGER).

Abstract

In order to achieve a better understanding of the impact of exercise on the concentration of serum free fatty acids (FFA) during post-exercise recovery, the purposes of this study were: (1) to determine the relationships between exercise intensity, total exercise energy expenditure, and the concentration of serum FFA during post-exercise recovery; (2) to examine the effects of exoge- nous glucose on post-exercise serum FFA and hormones controlling the FFA response; and (3) to examine the impact of acute exercise on hunger. Untrained, 12-h fasted, college-age males performed cycle ergometer exercise at exercise intensities ranging from 29 to 59% peak ‘VO₂ for total energy expenditures ranging from 162 to 320 kcal. Blood samples, hunger ratings, and metabolic indices were collected or measured before, during, and for 3 h post-exercise. In response to exercise of approximately 300 kcal, FFA was elevated for 3 h post-exercise. The FFA response was a function of total exercise energy expenditure, rather than exercise intensity, or combined effects of these factors. The response was associated with low insulin concentration but no changes were observed in blood glucose, glucagon, growth hormone, or cortisol. Glucose ingestion and infusion studies demonstrated that possible mechanisms con- tributing to the post-exercise FFA response included decreases in FFA re-esterification, increases in triglyceride hydrolysis, and decreases in sympathetic input to adipose tissue. Exercise caused a suppression of hunger for 2 h post-exercise which was a function of the combined effects of exercise intensity and total energy expenditure. An increase in core temperature may have contributed to the anorexigenic effect of exercise. In conclusion, exercise, performed in and followed by a period of fasting caused an elevation of FFA for 3 h during post-exercise recovery. The post-exercise recovery period should be considered an important phase in the physiological impact of exercise on the storage and utilization of fat.