Gender alters the effects of palmitate and oleate on fat oxidation and energy expenditure.

OBJECTIVE: Because estrogen and testosterone affect transcription factors regulating mitochondrial function, we assessed the effects of gender on the metabolic response to dietary palmitic acid (PA) vs. oleic acid (OA) in subjects participating in a previously described trial.

METHODS AND PROCEDURES: Adults (N = 43) were studied after following a baseline diet (PA = 8.4% kcal, OA = 13.1% kcal) and after undergoing one of two experimental diets: high PA (HI PA) (PA = 16.8%, OA = 16.4% kcal) (N = 21; 11 men) or high OA (HI OA) (PA = 1.7%, and OA = 31.4%) (N = 22; 11 men).

RESULTS: Relative to baseline, the rate of fatty acid (FA) oxidation (% resting energy expenditure(REE)) (mean +/- s.e.m.) increased in women on HI OA while decreasing on HI PA in the fed (+11.8 +/- 5.6% vs. -6.3 +/- 4.2%, P = 0.02) and fasting states (+13.4 +/- 4.2% vs. -12.7 +/- 6.9%, P = 0.047), but changes in men were not statistically significant. Daily energy expenditure changed only in men, increasing on HI OA and decreasing on HI PA (+66 +/- 61 kcal/day or 1.2 +/- 1.0 kcal/kg fat-free mass (FFM)/day vs. -266 +/- 78 kcal/day or -4.2 +/- 1.3 kcal/kg FFM/day, P = 0.004 and P = 0.007, respectively).

DISCUSSION: Increased dietary PA/OA caused decreased FA oxidation in women, in the fed and fasted states and decreased daily energy expenditure (DEE) in men.