The independent effects of dietary weight loss and aerobic training on high density lipoproteins and apolipoprotein A-I concentrations in obese men

Abstract

Several studies have demonstrated that high density lipoprotein cholesterol (HDL-C) is increased after either dietary weight loss or aerobic exercise training, but it is unclear whether the effects of these two interventions are separate and independent, or just related to the amount of weight or fat lost. The effect of dietary weight loss or aerobic training on apolipoprotein A1 (Apo-A-I) has not been extensively studied. In the present study we evaluated the effects of either dietary weight loss or aerobic exercise training on lipoproteins and Apo A-I, and assessed whether they are related to changes in body composition. Twenty-six obese, otherwise healthy, untrained, nonsmoking, male subjects were weight stabilized for ten days, during which maximal aerobic capacity, body composition, and fat cell size were measured. At the end of this ten-day period lipoproteins and Apo A-I were measured. Subjects were then randomized into either a dietary weight loss (n = 12) or aerobic exercise group (n = 14). At the end of three months the groups were restabilized and restudied. Although both groups lost weight, the weight loss was greater in the diet group (−13.1 v −2.8 kg, P < 0.001). Important differences in body composition were also detected after the two interventions with 25% of the total weight loss in the diet group coming from fat free mass. Significant decrements in triglyceride (−54 ± 67 mg/dl, P < 0.05), total cholesterol (−29 ± 27 mg/dL, P < 0.01), and non-HDL-C (−33 ± 27 mg/dL, P < 0.01) were found in the diet group only. HDL-C was increased after diet (4 ± 9 mg/dL, P < 0.05) or exercise (3 ± 3 mg/dL, P < 0.01) but Apo A-I increased only in the exercise group (7 ± 7 mg/dL, P < 0.01). Changes in body composition were not related to the observed changes in both HDL-C or Apo A-I in either group. It is concluded that dietary weight loss affects mainly the transport of cholesterol and triglyceride to cells as very low and low density lipoproteins. The observed increase in HDL-C was not accompanied by an increase in either HDL 2 or Apo A-I. Aerobic exercise appears to more directly affect the proposed HDL-mediated reverse cholesterol transport system by increasing both HDL-C and Apo A-I proportionately.