Effects of an American Heart Association step I diet and weight loss on lipoprotein lipid levels in obese men with silent myocardial ischemia and reduced high-density lipoprotein cholesterol

Abstract

Reduced plasma concentrations of high-density lipoprotein cholesterol (HDL-C) are a risk factor for coronary artery disease (CAD). In this study, we examined the sequential effects of an isocaloric American Heart Association (AHA) step I diet and a hypocaloric AHA step I diet (AHA step I diet + weight loss) on lipoprotein lipid levels in 14 middle-aged and older (60 ± 6 years, mean ± SD) obese (body mass index [BMI] > 27 kg/m 2) nondiabetic men with exercise-induced silent myocardial ischemia (SI) and reduced HDL-C levels (0.85 ± 0.14 mmol/L). Nine men of comparable age and obesity and with no evidence of exercise-induced ischemia that were evaluated longitudinally served as metabolic controls. In men with SI, after 3 months on the isocaloric AHA step I diet plasma triglyceride (TG) levels decreased by 26% (2.25 ± 0.66 to 1.67 ± 0.69 mmol/L, P < .005), cholesterol by 12% (5.24 ± 0.84 to 4.62 ± 0.78 mmol/L, P < .01), and low-density lipoprotein cholesterol (LDL-C) by 10% (3.40 ± 0.69 to 3.05 ± 0.70 mmol/L, P < .01). However, plasma HDL-C levels also decreased by 7% (0.85 ± 0.14 to 0.79 ± 0.13 mmol/L, P < .05). Subsequent weight loss (11 ± 4 kg) in conjunction with the AHA step I diet resulted in an additional decrease of 24% in TG ( P < .005), 10% in cholesterol ( P < .05), and 10% in LDL-C ( P < .05). Plasma HDL-C levels increased by 8% ( P < .01), thereby correcting the decline seen on the AHA step I diet alone. Postheparin hepatic lipase (HL) activity decreased with weight loss ( P < .005), with no significant change in lipoprotein lipase (LPL) activity. There were no significant changes in lipoprotein lipids or postheparin lipolytic activity in the metabolic controls. Therefore, in men with SI, the sequential interventions of an isocaloric AHA step I diet and an AHA step I diet with weight loss decreased plasma TG levels by 44% ( P < .0001), LDL-C levels by 18% ( P < .0001), and the LDL-C to HDL-C ratio by 19% ( P < .005), with no significant change in HDL-C levels. Additional treatment modalities that include supervised exercise programs and drug therapy may be warranted in older obese subjects whose HDL-C levels do not normalize with diet and weight-loss interventions alone.