A relatively high amount of fat in the diet may help keep a person's cholesterol levels in check, a small study suggests. And 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% 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% of calories from fat boosted participants' HDL levels.
To circulate in the blood, cholesterol must be attached to a protein, forming a complex called a lipoprotein. HDL (high-density lipoprotein) molecules carry cholesterol away from the arteries and to the liver to be cleared from the body.
The new findings suggest that adequate fat intake can help ward off heart disease by raising HDL.
These findings do not mean that people should be on a 50-percent fat diet. But they do indicate that moderation, and not tight restriction, is the way to go. That means getting about 30 to 35% of calories from fat - at or slightly more than the level health officials currently recommend.
The researchers 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, the researchers said it may in fact be the combination of lots of fat and too many calories that makes for unhealthy cholesterol profiles.
In the 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% of calories from fat.
The 19% 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 that of dieters on the high-fat one. What's more, the high-fat diet did not boost LDL cholesterol beyond the levels participants had on their regular diets.
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.
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