Objective: To determine the effects of exercise, without weight loss, on insulin sensitivity (S(I)), postheparin plasma lipase activity (PHPL), intravenous fat clearance rate (K(2)), and fasting lipids in sedentary adults.
Research design and methods: At baseline and after 6 months of walk training (intensity 45-55 or 65-75% heart rate reserve, frequency 3-4 or 5-7 days/week, duration 30 min/session), anthropometric indexes, S(I), PHPL, K(2), and fasting lipids were measured in 18 sedentary adults (12 women, 6 men; 51.9 +/- 5.8 years of age, BMI 28.9 +/- 4.6 kg/m(2)).
Results: Exercise increased S(I) (2.54 +/- 2.74 vs. 4.41 +/- 3.30 microU ml(-1) x min(-1), P < 0.005) and both lipoprotein lipase (LPL) (1890 +/- 1380 vs. 4926 +/- 1858 nEq free fatty acid [FFA]. ml(-1). h(-1)) and hepatic lipase (HL) activities (3326 +/- 1605 vs. 4636 +/- 1636 nEq FFA. ml(-1) x h(-1)) (both P < 0.001), without altering BMI, waist circumference, K(2), or fasting lipids. Correlations between changes in LPL and the total:HDL cholesterol ratio (r = -0.54) and changes in the LPL:HL ratio and waist circumference (r = -0.50) were significant (P < 0.05).
Conclusions: Exercise, without weight loss, increases S(I) and PHPL activity in previously sedentary adults, without changing K(2) or fasting lipid levels. Furthermore, increased LPL is associated with a decreased total:HDL ratio, and an increased LPL:HL ratio is associated with a decreased waist circumference. Therefore, even modest amounts of exercise in the absence of weight loss positively affect markers of glucose and fat metabolism in previously sedentary, middle-aged adults.