2.a. Lifestyle Trials
Rationale: Fourteen RCT articles that studied the effects of diet and/or physical activity on lipids were reviewed (365, 368, 370, 373, 380, 384, 399-406). Table III-1 summarizes RCTs in which diet alone was used to produce weight loss. Entries under percentage change were calculated as follows: the percentage change (value at the end of study minus the value at "baseline", divided by the value at baseline) was determined for the intervention group and the control group; the percentage change for the control group was then subtracted from the percentage change for the intervention group, giving the numerical value presented. When a run-in period was used, the baseline subtracted was the value at the end of the run-in, which was when the intervention began.
Reductions in body weight varied from 5 to 13 percent compared to the control group. The following changes in plasma lipids and lipoproteins were observed: total cholesterol, 0 to -18 percent; triglycerides, -2 to -44 percent; LDL-cholesterol, -3 to -22 percent; and HDL-cholesterol, -7 to +27 percent. Most of the trials were of sufficient duration to ensure that these changes were not the result of acute caloric deficit.
Table III-2 summarizes RCTs in which diet plus physical activity or physical activity alone was used to produce weight loss. Entries under percentage change were calculated as for Table III-1. Similar changes were observed as for diet alone, although there was perhaps a more consistent trend for all the lipid parameters with the combination of diet and physical activity and with physical activity alone.