Conjugated linoleic acid supplementation alters the 6-mo change in fat oxidation during sleep.
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.


METHODS
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 isotope-labeled oleate and palmitate.


RESULTS
Our substudy detected a difference in the change in fat utilization between the CLA (4 +/- 8 g) and placebo (-7 +/- 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: -3.3 +/- 2.6%; placebo: 0.3 +/- 5.7%). We also detected a difference in the change in energy expenditure during sleep (CLA: 0 +/- 38 kcal; placebo: -43 +/- 90 kcal). We did not detect a change in labeled dietary fat oxidation after 6 mo of CLA supplementation given with a breakfast meal.


CONCLUSIONS
Mixed isomer CLA supplementation, but not placebo, positively altered fat oxidation and energy expenditure during sleep.
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Rachel N
RN
Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI, USA.
Schoeller
Dale A
DA
Watras
Abigail C
AC
Nora
Elizabeth H
EH
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000328:Adult; D001481:Basal Metabolism / Q000187:drug effects* / Q000502:physiology; D002153:Calorimetry, Indirect / Q000379:methods; D019587:Dietary Supplements; D004311:Double-Blind Method; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D005260:Female; D006801:Humans; D044243:Linoleic Acids, Conjugated / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D050177:Overweight / Q000188:drug therapy / Q000378:metabolism; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D012450:Safflower Oil; D012890:Sleep / Q000502:physiology*