Background: Conjugated linoleic acid (CLA) is a family of positional and geometric isomers with 2 conjugated double bonds formed from linoleic acid and linolenic acid. CLA has a wide range of biological effects, including body fat reduction.
Objective: The aim of our study was to determine CLA's effects on energy expenditure, macronutrient utilization, and dietary fat oxidation in overweight adults after 6 mo of supplementation.
Design: We recruited 23 subjects from our main CLA efficacy study who were receiving either 4 g/d of 78% active CLA isomers (3.2 g/d: 39.2% cis-9,trans-11 and 38.5% trans-10,cis-12) or 4 g/d of safflower oil. Energy expenditure and substrate utilization were measured before and after 6 mo of CLA supplementation by using whole-room indirect calorimetry. Dietary fat oxidation was measured by using stable isotopeï¿½??labeled oleate and palmitate.
Results: Our substudy detected a difference in the change in fat utilization between the CLA (4 Â± 8 g) and placebo (ï¿½??7 Â± 11 g) groups during sleep after 6 mo of supplementation. In addition, the percentage of energy from protein was reduced during sleep in the CLA group (CLA: ï¿½??3.3 Â± 2.6%; placebo: 0.3 Â± 5.7%). We also detected a difference in the change in energy expenditure during sleep (CLA: 0 Â± 38 kcal; placebo: ï¿½??43 Â± 90 kcal). We did not detect a change in labeled dietary fat oxidation after 6 mo of CLA supplementation given with a breakfast meal.
Conclusion: Mixed isomer CLA supplementation, but not placebo, positively altered fat oxidation and energy expenditure during sleep.