A randomized trial analyzing the effect of a diet rich in SFA or PUFA on the lipid profile of subjects with normal-weight and subjects with obesity and elevated LDL-cholesterol

Summary Background: People with elevated cholesterol have an increased risk for developing cardiovascular disease (CVD). Lipid modifying diets, which reduces the intake of saturated fatty acids (SFA) and increases the intake of polyunsaturated fatty acids (PUFA) reduces the cholesterol and affects the risk for developing CVD. There are gaps in research about whether subjects with normal-weight (NW) and subjects with obesity (OB) respond differently to lipid-modifying diets. Objective: To investigate if there are differences in the changes in the lipid profile between weight stable, non-statin treated NW (BMI < 25 kg/m2) and subjects with OB (BMI 30-45 kg/m2) with elevated low-density lipoprotein cholesterol (LDL-C) eating a diet enriched with either SFA from butter or PUFA from soft margarine for six weeks. Method: A total of 71 men and women aged 18-70 years were randomized to one of the two diets. 23 NW and 14 OB were randomized to the SFA diet and 20 NW and 14 OB were randomized to the PUFA diet group. Butter and soft margarine was handed out to the participants, enough to supply them with a minimum portion of 24 grams butter and 25 grams soft margarine each day. The dietary intake was registered with a weighed seven days food registration at baseline and at the end of the study period. Measurements of the lipid profile, total cholesterol (TC), LDL-C, high-density lipoprotein cholesterol (HDL-C), triglycerides (TG) and Apolipoprotein B (Apo B) were measured at the screening, randomization visit and after four and six weeks. Results: The baseline values for TC and LDL-C for all the participants in the study were 6.5 mmol/L and 4.4 mmol/L. There was a significant between group difference in the mean change in TC after six weeks between NW and OB subjects in the SFA diet group (TC NW 7.1 mmol/l (SD 1.0) and TC OB 6.4 mmol/L (SD 1.3)), with a greater increase in TC for the NW (difference 0.4 mmol/L, 95 % CI 0.0,0.8, p= 0.04). In an adjusted linear regression analysis there was a significant effect for the variable “diet group” (all p≤0.001) and a trend for an effect of the interaction variable between BMI and diet group on the change in TC, LDL-C and Apo B. For the NW in the SFA diet group there were significant within group changes with an increase in TC, LDL-C, HDL-C and Apo B. For the OB subjects in the SFA diet group there were no significant changes. For both the NW and OB subjects in the PUFA diet group there were significant within group changes with a reduction in TC, LDL-C and Apo B. Significant changes in the diet after six weeks were attained according to the planned dietary intervention, with a different in 9.1 E% from SFA and 4.2 E% from PUFA between the NW and 10.2 E% from SFA and 5.4 E% from PUFA between the OB subjects in the two diet groups. Conclusions: For the subjects that increased their intake of SFA it was a difference in the response in TC between NW and OB. For NW subjects with elevated LDL-C increasing their intake of SFA (19.6 E%) lead to a significant increase in TC, LDL-C, HDL-C and Apo B while increasing the intake of PUFA (9.9 E%) gave beneficial changes in TC, LDL-C, Apo B and TG. For the OB subjects with elevated LDL-C, an increased intake of SFA (20.4 E%) did not significant change the lipid profile, while increasing the intake of PUFA (10.1 E% lead to a reduction in TC, LDL-C and Apo B. A failure to include enough participants with obesity reduced the strength of these conclusions