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

Background: Low-fat diets can increase plasma triacylglycerol and reduce HD L cholesterol. Changes in energy intake and body weight can influence the l ipoprotein response. Objective: We sought to prospectively examine the effects of euenergetic an d ad libitum dietary fat restriction on plasma lipoproteins in healthy post menopausal 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. Thereaft er, participants followed an ad libitum 15%-fat diet for 8 mo; 54 women com pleted the intervention. Results: During the controlled euenergetic diet, plasma triacylglycerol inc reased from 1.70 +/- 0.10 to 2.30 +/- 0.16 mmol/L, total cholesterol decrea sed from 5.87 +/- 0.13 to 5.53 +/- 0.13 mmol/L, LDL cholesterol decreased f rom 3.41 +/- 0.10 to 2.87 +/- 0.10 mmol/L, HDL cholesterol decreased from 1 .76 +/- 0.08 to 1.50 +/- 0.08 mmol/L, and apolipoprotein (apo) A-I decrease d from 5.11 +/- 0.14 to 4.78 +/- 0.14 mmol/L (P < 0.0001 for all changes). Hormone replacement therapy did not affect the relative change in HDL chole sterol. Plasma glucose, insulin, hemoglobin A(1C) free fatty acid, and apo B concentrations did not change significantly. During the ad libitum 15%-fa t diet, participants lost 4.6 +/- 0.4 kg. Plasma triacylglycerol and LDL ch olesterol returned to baseline values (1.77 +/- 0.12 and 3.31 +/- 0.08 mmol /L, respectively), whereas HDL cholesterol and apo A-I remained low (1.40 /- 0.08 and 4.82 +/- 0.18 mmol/L, respectively). HDL cholesterol and apo A- I concentrations stabilized in subjects who were not receiving hormone repl acement therapy but continued to decline in women who were receiving hormon e therapy. Conclusions: The ad libitum 15%-fat diet resulted in significant weight los s. The euenergetic but not the ad libitum diet caused hypertriacylglycerole mia. HDL cholesterol decreased during both low-fat diets.