Metabolic effects of caffeine in humans: lipid oxidation or futile cycling?

摘要: Background: Caffeine ingestion stimulates both lipolysis and energy expenditure. Objectives: Our objectives were to determine whether the lipolytic effect of caffeine is associated with increased lipid oxidation or futile cycling between triacylglycerol free fatty acids (FFAs) effects are mediated via sympathetic nervous system. Design: Respiratory exchange [1- 13 C]palmitate used trace FFA turnover in 8 healthy, young men for 90 min before 240 after placebo, (10 mg/kg), during -adrenoceptor blockade. Results: During fasting conditions, there few differences measured variables 3 tests. steady state conditions (last hour test) caffeine, 2-fold (P 0.005), mean (SEM) thermic was 13.3 2.2% 0.001), which greater than placebo After oxidative disposal 44% (236 21 340 16 mol/min), whereas nonoxidative 2.3-fold (455 66 1054 242 mol/min; P 0.01). In postabsorptive 34% lipids oxidized 66% recycled. expenditure 13% doubled lipids, 24% 76% -Adrenoceptor blockade decreased, but did not inhibit, these variables. Conclusions: Many, all, The on mobilization resting can be interpreted 2 ways: alone insufficient drive oxidation, large increments result small oxidation. Am J Clin Nutr 2004;79:40–6.