Low-Fat May Not Be Best for Heart

A relatively high amount of fat in the diet may be a boon to a healthy person's cholesterol levels, a small study suggests. On the other hand, limiting fat intake too much could have the opposite effect.

Researchers at the State University of New York at Buffalo found that when 11 healthy but sedentary adults followed a very low-fat diet (19 percent of calories from fat) for three weeks, they saw a drop in their HDL cholesterol -- the "good" cholesterol believed to protect against heart disease.

In contrast, three weeks on a diet that provided 50 percent of calories from fat boosted participants' HDL levels, according to findings published in the Journal of the American College of Nutrition.

To circulate in the blood, cholesterol must be attached to a protein, forming a complex called a lipoprotein. HDL, or high-density lipoprotein, molecules carry cholesterol away from the arteries and to the liver to be cleared from the body. Experts believe that an HDL level of 60 or more helps lower the risk of heart disease, while a level lower than 40 raises the risk.

The new findings suggest that adequate fat intake can help ward off heart disease by raising HDL.

"That isn't to say we think everyone should be on a 50-percent fat diet," study co-author Dr. David R. Pendergast stated.

But, he said, the findings do indicate that moderation, and not tight restriction, is the way to go. According to Pendergast, that means getting about 30 to 35 percent of calories from fat -- at or slightly more than the level health officials currently recommend.

But he also stressed the importance of calorie balance, which means eating only enough to meet the body's calorie expenditure. Fat has more calories per gram than either carbohydrates or protein, and if a person takes in more calories as a result of eating more fat, weight gain may follow.

While saturated fat is blamed for raising "bad" LDL cholesterol levels, Pendergast said it may in fact be the combination of lots of fat and too many calories that makes for unhealthy cholesterol profiles.

In his team's study, the high-fat diet -- rich in foods such as red meat and olive oil -- provided roughly the same number of daily calories as participants' regular diets, which contained about 30 percent of calories from fat.

The 19-percent low-fat diet had fewer calories, and men and women in the study lost a small amount of weight while following it. Their HDL levels, however, were significantly lower on this diet than on the high-fat one-an average of 54 milligrams per deciliter (mg/dL), versus 63 mg/dL, Pendergast and his colleagues found.

What's more, the high-fat diet did not boost LDL cholesterol beyond the levels participants had on their regular diets.

Although the men and women followed each diet for only three weeks, Pendergast said he does not think the cholesterol effects are "transient."

He and his colleagues had previously conducted a similar study with endurance runners, in which a very low fat intake had negative effects on HDL cholesterol and on immune function. Pendergast said this research suggests that both healthy, sedentary people and healthy athletes are "probably not well served" by diets very low in fat.

Whether high- and low-fat diets have the same effects in obese individuals or those with cardiovascular disease is not yet clear, he noted.

As for why a high-fat, calorie-conscious diet might bump up HDL levels, one theory is that dietary fat leads to higher levels of the chief HDL transporter protein, ApoA1.

SOURCE: Journal of the American College of Nutrition, April 2004.

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