Changes in plasma lipoproteins during low-fat, high-carbohydrate diets: effects of energy intake

Background: Low-fat diets can increase plasma triacylglycerol and reduce HDL cholesterol. Changes in energy intake and body weight can influence the lipoprotein response. Objective: We sought to prospectively examine the effects of euenergetic and ad libitum dietary fat restriction on plasma lipoproteins in healthy postmenopausal women. Design: Participants first received a controlled euenergetic diet in which dietary fat was reduced stepwise from 35% to 25% to 15% over 4 mo. Thereafter, participants followed an ad libitum 15%-fat diet for 8 mo; 54 women completed the intervention. Results: During the controlled euenergetic diet, plasma triacylglycerol increased from 1.70 [+ or -] 0.10 to 2.30 [+ or -] 0.16 mmol/L, total cholesterol decreased from 5.87 [+ or -] 0.13 to 5.53 [+ or -] 0.13 mmol/L, LDL cholesterol decreased from 3.41 [+ or -] 0.10 to 2.87 [+ or -] 0.10 mmol/L, HDL cholesterol decreased from 1.76 [+ or -] 0.08 to 1.50 [+ or -] 0.08 mmol/L, and apolipoprotein (apo) A-I decreased from 5.11 [+ or -] 0.14 to 4.78 [+ or -] 0.14 mmol/L (P [is less than] 0.0001 for all changes). Hormone replacement therapy did not affect the relative change in HDL cholesterol. Plasma glucose, insulin, hemoglobin A[.sub.1C] free fatty acid, and apo B concentrations did not change significantly. During the ad libitum 15%-fat diet, participants lost 4.6 [+ or -] 0.4 kg. Plasma triacylglycerol and LDL cholesterol returned to baseline values (1.77 [+ or -] 0.12 and 3.31 [+ or -] 0.08 mmol/L, respectively), whereas HDL cholesterol and apo A-I remained low (1.40 [+ or -] 0.08 and 4.82 [+ or -] 0.18 mmol/L, respectively). HDL cholesterol and apo A-I concentrations stabilized in subjects who were not receiving hormone replacement therapy but continued to decline in women who were receiving hormone therapy. Conclusions: The ad libitum 15%-fat diet resulted in significant weight loss. The euenergetic but not the ad libitum diet caused hypertriacylglycerolemia. HDL cholesterol decreased during both low-fat diets. Am J Clin Nutr 2000;71:1439-47. KEY WORDS Low-fat diet, lipoproteins, postmenopausal women, high-carbohydrate diet, lipoprotein response, triacylglycerol, HDL cholesterol, high-density-lipoprotein cholesterol, triglycerides, weight reduction, hormone replacement therapy, apolipoprotein A-I, free fatty acids, glucose, insulin, hemoglobin [A.sub.1C]