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'Yo-yo' dieting may cut women's levels of good cholesterol

Wednesday, November 01, 2000

By Byron Spice, Science Editor, Post-Gazette

Health authorities have long warned that people who repeatedly lose weight on special diets only to gain it all back -- a practice called weight cycling, or "yo-yo dieting" -- could be risking their health. But no one has been able to show exactly how this harm occurs.

Heart disease researchers now have come up with a possible culprit: lower levels of high density lipoproteins, or HDL, the so-called "good" cholesterol.

In a federally sponsored study of almost 500 women, researchers from four institutions found that women who were weight cyclers -- those who lost and regained 10 pounds or more at least three times -- had lower blood levels of HDL than non-cyclers. Weight cyclers who were obese, with a body mass index of 30 or more, had the lowest HDL levels. Non-cyclers with BMIs below 30 had the highest HDL levels.

In between those extremes, the thinner women who were yo-yo dieters had no advantage over obese women who maintained a stable weight. Both types had similar HDL levels.

A woman who stands 5 feet, 6 inches tall and weighs 186 pounds would have a BMI of 30. The ideal weight for this woman would be 131 pounds, or a BMI of 21.

High levels of HDL are considered beneficial because they reduce the buildup of fatty deposits in the coronary arteries. Low density lipoproteins, the "bad" cholesterol, has the opposite effect.

"To my knowledge, this is the first time we're seeing this association" between yo-yo dieting and lower HDL levels, said Marian Olson, an epidemiologist at the University of Pittsburgh Graduate School of Public Health and the study's lead author.

It's intriguing and worthy of further study, she added, though this study doesn't prove that weight cycling necessarily caused the HDL variation.

The findings appear in this month's issue of the Journal of the American College of Cardiology.

In Olson's statistical analysis, the association between HDL and weight cycling persisted even after taking into account such known heart disease risk factors as body mass index, excess abdominal fat, smoking, lack of exercise, alcohol intake, hormone replacement therapy, diabetes and race.

"We know that HDL is a significant risk factor among women," said Dr. Daniel Edmundowicz, a preventive cardiologist at the UPMC Cardiovascular Institute. So if yo-yo dieting did decrease HDL levels, this might explain why weight cyclers seem to have a greater risk of heart disease, he added.

But it's possible that the lower HDL levels were caused by something other than just repeatedly gaining and losing weight.

For instance, Edmundowicz said many weight cyclers are perpetual dieters who may favor low-fat diets; these low-fat diets can reduce HDL levels.

The study results do not suggest that obese people should not try to lose weight, Olson and Edmundowicz agreed.

They do support the notion the best way to lose weight is not by crash or fad diets, but to lose it gradually by making changes in diet and exercise that can be maintained for a lifetime.

Olson analyzed information gathered from 485 women enrolled in the Women's Ischemia Syndrome Evaluation study.

All were women who underwent coronary angiography because they were suffering chest pains. Of those women, 130 were yo-yo dieters.

The fact that all of the women had or were suspected of having heart disease may also limit the degree to which the findings can be generalized to the entire population, she acknowledged.

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