Thermogenesis in humans during overfeeding with medium-chain triglycerides.
Level 2 - randomized trial
Double-blind controlled crossover trial in humans
PubMed 2739575 · doi:10.1016/0026-0495(89)90101-7
What was done
Ten male volunteers (ages 22 to 44) were overfed at 150% of estimated energy requirements with liquid formula diets containing 40% of fat as either medium-chain triglycerides (MCT) or long-chain triglycerides (LCT). Each participant was studied for one week on each diet in a double-blind crossover design. Measurements included resting metabolic rate (RMR), thermic response to food (TEF) after a 1,000 kcal meal on day 1 and day 5, and energy expenditure during a 20-hour continuous enteral infusion on day 7.
What was found
Resting metabolic rate did not change during either week of overfeeding. Post-meal TEF on day 1 after a 1,000 kcal meal was higher with MCT than LCT (8 ± 0.8% vs 5.8 ± 0.8% of ingested energy; P < .05). After five days of overfeeding, TEF from the 1,000 kcal MCT meal increased significantly to 12 ± 1.3%, whereas the LCT meal was unchanged (6.6 ± 1.0%). During 20-hour continuous enteral infusion on day 7, energy expenditure was significantly higher with the MCT diet than the LCT diet (15.7 ± 1.7% vs 7.3 ± 0.9% of ingested energy; P < .05).
Why it matters
Surplus energy derived from medium-chain triglycerides stimulates higher thermogenesis than long-chain triglycerides, indicating that MCT excess is stored with lower energetic efficiency.
Limits
The study was very small (n=10) and included only adult males. The intervention lasted only one week per arm and evaluated liquid formula diets, so findings may not generalize to long-term energy balance, women, or typical solid-food diets.