Effect of gender on lipid kinetics during endurance exercise of moderate intensity in untrained subjects

Jun 18, 2002American journal of physiology. Endocrinology and metabolism

How gender affects fat metabolism during moderate exercise in untrained people

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Abstract

The total increase in glycerol and free fatty acid rate of appearance in plasma during exercise was approximately 65% greater in women than in men.

Glycerol and free fatty acid levels in women during exercise were 317 +/- 40 and 652 +/- 46 micromol/kg, respectively, compared to 195 +/- 33 and 453 +/- 70 micromol/kg in men.
Both total fatty acid oxidation rates were similar between men and women during exercise.
The relative contribution of plasma free fatty acids to total fatty acid oxidation was higher in women (76 +/- 5%) than in men (46 +/- 5%).
Increased lipolysis of adipose tissue triglycerides during moderate-intensity exercise may lead to greater fatty acid availability and uptake in women.
Total fat oxidation remained equal across genders due to a decrease in the oxidation of fatty acids from nonplasma sources in women.

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We evaluated lipid metabolism during 90 min of moderate-intensity (50% VO(2) peak) cycle ergometer exercise in five men and five women who were matched on adiposity (24 +/- 2 and 25 +/- 1% body fat, respectively) and aerobic fitness (VO(2) peak: 49 +/- 2 and 47 +/- 1 ml x kg fat-free mass(-1) x min(-1), respectively). Substrate oxidation and lipid kinetics were measured by using indirect calorimetry and [(13)C]palmitate and [(2)H(5)]glycerol tracer infusion. The total increase in glycerol and free fatty acid (FFA) rate of appearance (R(a)) in plasma during exercise (area under the curve above baseline) was approximately 65% greater in women than in men (glycerol R(a): 317 +/- 40 and 195 +/- 33 micromol/kg, respectively; FFA R(a): 652 +/- 46 and 453 +/- 70 micromol/kg, respectively; both P < 0.05). Total fatty acid oxidation was similar in men and women, but the relative contribution of plasma FFA to total fatty acid oxidation was higher in women (76 +/- 5%) than in men (46 +/- 5%; P < 0.05). We conclude that lipolysis of adipose tissue triglycerides during moderate-intensity exercise is greater in women than in men, who are matched on adiposity and fitness. The increase in plasma fatty acid availability leads to a greater rate of plasma FFA tissue uptake and oxidation in women than in men. However, total fat oxidation is the same in both groups because of a reciprocal decrease in the oxidation rate of fatty acids derived from nonplasma sources, presumably intramuscular and possibly plasma triglycerides, in women.

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Effect of gender on lipid kinetics during endurance exercise of moderate intensity in untrained subjects

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