Fish oil supplementation does not alter energy efficiency in healthy males.
OBJECTIVE
Fish oil (FO) supplementation prevents the development of obesity and insulin resistance, and upregulate the expression of UCP3 in skeletal muscle in rodents. This may represent indirect evidence that FO promotes fat oxidation and/or alter energy efficiency. The aim of this study was to evaluate whether such effects can be observed in humans. The metabolic effects of FO were assessed during exercise in order to obtain a direct measurement of energy efficiency.


METHODS
Eight healthy male volunteers were studied with and without supplementation with 7.2 g/day FO (including 1.1 g/day eicosopentaenoic acid and 0.7 g/day decosahexaenoic acid) during 14 days. Their VO(2 max) was measured on cycle ergometer. Thereafter, energy metabolism (substrate oxidation, energy expenditure and energy efficiency) was assessed during a 30 min cycling exercise at 50% VO(2 max) performed 2 h 30 after a standardized, high carbohydrate breakfast.


RESULTS
VO(2 max) was 38.6+/-2.2 after FO and 38.4+/-2.0 (mL x kg(-1) x min(-1)) in control conditions (NS). Basal plasma glucose, insulin and NEFA concentrations, and energy metabolism were similar with FO and in controls. During exercise, the increases in plasma NEFA concentrations, energy expenditure, glucose and lipid oxidation, and the decreases in glycaemia and insulinemia were not altered by FO intake. Energy efficiency was 22.4+/-0.6% after FO vs 21.8+/-0.7% in controls. In order to ascertain that the absence of effects of FO was not due to consumption of a carbohydrate meal immediately before exercise, 4 of the 8 subjects were re-studied in fasting conditions, FO also failed to alter energy efficiency in this subset of studies.


CONCLUSIONS
FO supplementation did not significantly alter energy metabolism and energy efficiency during exercise in healthy humans.
Bortolotti
Murielle
M
Department of Physiology, University of Lausanne, 7 rue du Bugnon, 1005 Lausanne, Switzerland.
Tappy
Luc
L
Schneiter
Philippe
P
D000328:Adult; D001481:Basal Metabolism / Q000187:drug effects* / Q000502:physiology; D001642:Bicycling / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism*; D018592:Cross-Over Studies; D019587:Dietary Supplements; D004734:Energy Metabolism / Q000187:drug effects* / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005395:Fish Oils / Q000008:administration & dosage*; D006801:Humans; D007328:Insulin / Q000097:blood; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption
D001786:Blood Glucose; D005230:Fatty Acids, Nonesterified; D005395:Fish Oils; D007328:Insulin