Background: The well-established relation between changes in dietary fatty acids and plasma lipids has been determined in energy-balance states. Whether this relation is altered in states of energy restriction and active weight loss is not clear.
Objective: The objective of this 12-wk study was to compare the time course of lipid changes and other cardiovascular risk factors in 3 energy-restricted diets (all 6500 kJ) with different total fat and fatty acid compositions.
Design: Sixty-two subjects with a body mass index (in kg/m(2)) >24 were stratified into 1 of 3 parallel dietary intervention groups: 1) a very-low-fat (VLF) diet (10% of energy from fat; 3% from saturated fat), 2) a high-saturated-fat (HSF) diet (32% of energy from fat; 17% from saturated fat), and 3) a high-unsaturated-fat (HUF) diet (32% of energy from fat; 6% from saturated fat).
Results: After 12 wk, LDL cholesterol decreased by 0. 66 +/- 0.11 (mean +/- SEM) and 0.68 +/- 0.12 mmol/L ( approximately 20%) with the VLF and HUF diets, respectively, compared with a decrease of only 0.24 +/- 0.11 mmol/L (7%) with the HSF diet (P < 0.02 between groups). Diet affected the time course of changes in HDL cholesterol with both high-fat diets, resulting in smaller reductions in HDL cholesterol at weeks 1 (P = 0.0004) and 4 (P = 0.02); however, these differences were no longer apparent by 12 wk. Overall weight loss was 8.6 +/- 0.4 kg (9.7%) and waist circumference decreased by 7.3 +/- 5 cm (8%) for the combined groups, with no significant differences between diets.
Conclusions: Significantly greater decreases in LDL cholesterol during active weight loss are achieved with diets low in saturated fatty acids. Changes in HDL cholesterol between diets appear dependent on both the fat content of the diet and the duration of energy restriction.