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Test Identifies Men Who Respond Well to Low-Fat Diets, Study Says

July 15, 1996

PORTSMOUTH, N.H. (AP) _ A test focusing on ``bad cholesterol″ particles can identify men who are most likely to cut their heart disease risk through a very low-fat diet, a researcher said Monday.

Preliminary research also suggests that for some men, such a diet may actually raise heart disease risk.

About one-third of men have unusually small LDL cholesterol particles, a sign of a wider cluster of abnormalities that gives them an increased heart disease risk. Their cholesterol profile showed substantial improvement with a very low-fat diet in recent studies, said Dr. Ronald Krauss.

But in the same studies, men with normal-sized particles _ the trait seen in most men _ showed no benefit as a group.

Still, individuals in this group showed wide variation in their response, and the test can’t predict with certainty whether an individual will improve his cholesterol profile on a very low-fat diet of 20 percent to 25 percent or less of calories from fat, Krauss stressed.

Krauss, who is chairman of the American Heart Association’s Nutrition Committee, said the test may be marketed later this year, though he has no financial interest in it.

He discussed the work in an interview before presenting it at a meeting sponsored by the association.

Krauss said research suggests that in some men with normal-sized particles, a very low-fat diet can cause changes in the cholesterol profile that indicate an increased heart disease risk.

In one study, 36 out of 87 men with normal-sized particles switched to the small-particle abnormalities when their dietary fat was lowered from 46 percent of calories from fat to 24 percent. One sign of the switch was a rise in their ratio of total cholesterol to ``good″ HDL cholesterol, which implies a higher heart disease risk.

That might have been caused by the high-carbohydrate portion of the diet, Krauss said.

In the general population, maybe 20 percent to 25 percent of men might show the switch to the small-particle pattern, Krauss said. Right now, these men can’t be identified ahead of time, but gene testing might allow that in the future, he said.

Scientists haven’t yet studied whether this switch is in fact harmful, he said. And some benefits of a low-fat diet, such as weight loss, were not studied in the research, he said.

The average American gets 35 percent of calories from fat. The heart association recommends 30 percent or less.

The work so far has been done with healthy, normal-weight men who had normal cholesterol levels. Researchers haven’t done similar work in women because a relatively small percentage of them have the small-particle pattern, he said.

It’s not clear how well the test would predict response to diet in untested groups, like people who are fat or have high cholesterol.

But the findings are a preliminary step toward developing a series of tests that someday might let doctors identify who should go on a very low-fat diet, Krauss said. The overall idea is to test for genetic predispositions, he said.

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