But that was only the case among people who stuck with the diet study over a few months. More than one-fifth of people dropped out when they couldn't tolerate the supplement's taste, texture and side effects.

Researchers have explored the potential of seaweed as an appetite suppressant, but so far products haven't panned out.

"There have been problems in the past to develop something (that tastes) acceptable," said Dr. Arne Astrup, one of the study's authors from the University of Copenhagen and a member of the advisory board to S-Biotek, a Danish company that provided funding for the study.

Previous seaweed-based supplements were slimy and caused bloating, and they also had a fishy taste. The new supplement used in this study is less unpleasant -- but there's still room for improvement, said Astrup.

The supplement is based on the seaweed extract alginate, a thickening agent and a common ingredient in foods like soups and jellies. It's also increasingly used by the weight-loss industry, marketed as an appetite suppressant.

Packaged in powder form and mixed with liquid, alginate expands in the stomach to form a thick gel, mimicking the effect of a large meal.

"This gel is really like a pudding that will last in the stomach for hours, gradually degrading and disappearing," Astrup said.

For the study, the researchers randomly divided 96 generally healthy but obese people, aged 20 to 55, into two groups.

One group was given packets of the gel supplement, containing 15 grams of fiber, and the other got a seaweed-free placebo drink. Neither the researchers nor the participants knew who was receiving the seaweed supplement.

In terms of calories, flavor and appearance, the placebo and treatment drink were identical.

For three months, study participants drank the supplements, dissolved in two cups of water, 30 minutes before each meal. They were also told to cut back on calories. By the end of the trial, sixteen people had dropped out of the study, including 10 out of 48 from the seaweed group, according to findings published in the American Journal of Clinical Nutrition.

Among people who stuck with the trial, those on the fiber supplement lost 15 pounds, on average, compared to 11 pounds in the placebo group. But when all 96 original participants were included in the analysis, the researchers found no significant difference in weight loss between the two treatment groups.

TREAT FINDINGS ‘WITH CAUTION'

Previous studies have shown eating a high-fiber diet can help reduce the hunger pangs that may lead to over-eating and derail a healthy diet plan.

Still, the new results should be treated with caution, according to Dr. Maria Vazquez Roque, who has worked on alginate-based gels at the Mayo Clinic in Jacksonville, Florida, but was not involved in the study. Just looking at the effect of the supplement on people who finished the treatment can bias the findings, she said.

For Mette Kristensen, one of the study's authors, the message seems clear: "If you actually comply with the treatment, you do have the improvement in weight loss."

However, effects on blood pressure were less promising. Systolic blood pressure -- the top number on a blood pressure reading -- fell by almost six points on average in the placebo group over the 12-week study, but by just over one point in the treatment group. At times during the trials, systolic blood pressure increased in the alginate group by one to two points.

According to the researchers, the higher sodium content of the alginate drink -- a little over one gram per dose, or about half a teaspoon of salt -- could have offset any potential blood-pressure reducing effect of the supplement. The American Heart Association recommends that adults eat less than 1.5 g of sodium per day.

Questions remain about the safety of the fiber supplement over the long term. Five people taking the fiber gel left the study due to problems with stomach bloating, nausea and diarrhea. Two people taking a placebo supplement, which didn't contain the seaweed fiber, experienced similar problems.

There are many different types of alginate, said Richard Mattes, who has studied the effect of alginate fiber on appetite at Purdue University in West Lafayette, Indiana -- so the trick is to find the right alginate in the right dose.

And just feeling less hungry due to a supplement won't make you lose weight unless you eat fewer calories, said Mattes, who was not involved in the new study.

The research group is working on a new supplement that uses 80 percent less alginate, with less sodium, better taste and fewer side effects than the current formula, Astrup told Reuters Health.

Alginate as an aid to weight loss is already commercially available in pill form and costs around $45 for a seven-day supply. These supplements are not regulated by the Food and Drug Administration, said Vazquez Roque.

SOURCE: bit.ly/LSuLvS American Journal of Clinical Nutrition, online May 30, 2012.

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