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Reason for Rebound Weight Gain Found
posted 01/12/04

Insulin resistance one of the culprits for weight gain after losing weight.

Plasma levels of norepinephrine, insulin, and leptin can help to predict which patients will rebound after a successful weight loss program, a new study suggests.

Patients with hypertension also appear to be at risk of rebound weight gain, said Kazuko Masuo, MD, PhD, from the Department of Geriatrics at Osaka University Graduate School of Medicine in Suita City, Japan. She reported the results last month at the American Heart Association (AHA) Scientific Sessions.

"The idea that a simple blood test can identify those that will yo-yo — before they even start their diet — is a new concept," said Robert H. Eckel, MD, chair of the AHA's Nutrition, Physical Activity and Metabolism Council and professor of medicine at the University of Colorado Health Sciences Center in Denver. "Identification of these people will help us to help them long-term."

About two thirds of American adults are overweight or obese, according to the most recent government statistics. But it's not for lack of trying: Experts estimate that up to two thirds of women and half of men are on a diet at any given time.

"Part of the problem is that so many of these people are repeat dieters," said Dr. Eckel, who moderated a discussion of the new findings. Studies suggest that as many as two in three dieters are back on the merry-go-round within a year, he said.

It is important to note, Dr. Masuo said, that the rebound rate is high even if dieters adhere to their weight loss regimens.

In the study, the researchers followed 52 obese young men with normal blood pressure and 61 obese men with hypertension who were on a low-calorie diet. As part of their weight loss regimen, all the participants exercised for an hour each day.

At baseline, mean body mass index (BMI) of patients was 27.9 kg/m² in the obese normotensive group and 28.1 kg/m² in the obese hypertensive group. Blood pressure was an average of 131/83 mm Hg in the obese normotensive group and 171/106 mm Hg in the obese hypertensive group.

At six months, about two thirds of the men in both groups had successfully lost at least 10% of their body weight.

But by two years later, only 51% of the successful dieters with high blood pressure had kept the weight off compared with 70% of those with normal blood pressure, Dr. Masuo reported.

When both groups of patients were analyzed together, those who rebounded tended to have higher blood pressure at baseline: 146/99 mm Hg compared with 136/89 mm Hg for those who did not rebound (P < .05), the study showed. Rebound was defined as more than a 10% increase in BMI at 24 months compared with BMI at six months.

Baseline plasma norepinephrine levels were 302 pg/mL in the patients who rebounded compared with 240 pg/mL in those who did not (P < .05), the study showed.

Those who rebounded — regardless of blood pressure — also tended to have higher levels of plasma insulin at the beginning of the study: 10.8 µU/mL vs. 7.1 µU/mL for the successful long-term dieters (P < .05).

Also, baseline plasma leptin levels were 19.5 ng/mL in the group that rebounded compared with 28.2 ng/mL in those who did not (P < .01), Dr. Masuo said.

The results suggest that sympathetic overactivity and insulin resistance contribute to rebound after weight loss, she said.

"If we could find how to improve the sympathetic nervous sensitivity of [receptors that mediate thermogenesis and weight loss during sympathetic activity], this would be beneficial in obesity and obesity-related hypertension," Dr. Masuo said.

Source: Diabetes In Control.com: AHA 2003 Scientific Sessions: Abstract 3049.

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