November 12, 1997

Long-term Cholesterol-Lowering Effects of 4 Fat-Restricted Diets in Hypercholesterolemic and Combined Hyperlipidemic MenThe Dietary Alternatives Study

Author Affiliations

From the Northwest Lipid Research Clinic (Drs Knopp and McCann and Mss Walden, Retzlaff, and Dowdy), Department of Medicine (Drs Knopp and Albers and Mss Walden, Retzlaff, and Dowdy), and Cardiovascular Behavioral Medicine Program, Department of Psychiatry and Behavioral Sciences (Dr McCann), University of Washington, and Boeing Medical Department (Drs Gey and Cooper), Seattle, Wash.
Dr Cooper died October 8, 1995.

JAMA. 1997;278(18):1509-1515. doi:10.1001/jama.1997.03550180059038

Context.  —The long-term effect of aggressively vs moderately fat-restricted diets has not been studied extensively in free-living subjects with different types of hyperlipidemia.

Objective.  —To compare the cholesterol-lowering effects of 4 levels of dietary fat intake restriction after 1 year.

Desing.  —Randomized, parallel, comparison trial.

Setting.  —Male employees of a large industry.

Participants.  —A total of 444 men had low-density lipoprotein cholesterol (LDLC) levels above the 75th age-specific percentile. Subjects with triglyceride (TG) levels less than the 75th age-specific percentile were defined as hypercholesterolemic (HC) and those with TG levels at or above the 75th age-specific percentile were defined as combined hyperlipidemic (CHL).

Interventions.  —Hypercholesterolemic subjects were randomized to diets 1, 2, 3, and 4 taught to contain 30%, 26%, 22%, and 18% fat, and the CHL subjects were randomized to diets 1,2, and 3. All 4 diets were taught to subjects and spouses or partners in 8 weekly 2-hour classes.

Main Outcome Measures.  —Plasma lipoprotein levels after 1 year.

Results.  —Fat intake after 1 year declined from a mean of 34% to 36% of energy to 27%, 26%, 25%, and 22% in the 4 HC diet groups and 28%, 26%, and 25% in the 3 CHL diet groups. Mean±SD percent LDL-C reductions were 5.3%±16.2%, 13.4%±12.6%, 8.4%±11.2%, and 13.0%±15.7% in the HC diet groups and 7.0%±16.2%, 2.8%±15.8%, and 4.6%±13.5% in the CHL diet groups (P<.01 in all but 1 instance). Apoprotein B levels decreased 8.6%, 10.7%, 4.3%, and 5.3% in the HC groups and 14.6%, 11.4%, and 9.9% in the CHL groups (P<.05-.01 in each instance). Triglyceride levels increased significantly in subjects following HC diets 3 and 4, 21.7% and 38.7% (P<.05 and.01), but not in any CHL subjects. High-density lipoprotein cholesterol decreased 2.8% and 3.2% in subjects on HC diets 3 and 4, respectively (P<.05 in both cases).

Conclusions.  —After 1 year, moderate restriction of dietary fat intake attains meaningful and sustained LDL-C reductions in HC subjects and apoprotein B reductions in both HC and CHL subjects. More extreme restriction of fat intake offers little further advantage in HC or CHL subjects and potentially undesirable effects in HC subjects.