Plasma free fatty acid response to exercise in obese humans

The effect of prolonged (4 hours) exercise on the concentration of plasma FFA was followed on 5 control subjects and on 4 obese patients. The response of plasma FFA was related to the energy expenditure measured as O 2 consumption. Plasma FFA increased during exercise to about the same value in both groups. When obese patients received a hypocaloric diet or entered a prolonged period (up to 26 days) of starvation, the resting value of FFA increased, but the final exercise value was the same as when they were on normocaloric diet. In the follow-up period, on close to normal caloric intake, the FFA returned to its baseline value, but the response to exercise was considerably depressed. While on hypocaloric diet or on starvation, the work RQ's were in the range of 0.71–0.74. Exercise failed to increase the urinary nitrogen output to any appreciable extent. It has been concluded (a) that our obese patients could readily mobilize FFA from their fat depots, in response to exercise; (b) that fat oxidation played a predominant role in their exercise metabolism; and (c) that even after prolonged starvation the participation of protein metabolism was negligible.