The Product: Experts have been saying for years that there's no such thing as a magic pill for weight loss. But who knows? They used to think no pill could treat bacterial pneumonia or erectile dysfunction. At a time when scientists are unlocking new secrets about our appetites and metabolism, it seems at least remotely plausible that the secret to a slimmer body could someday fit into a capsule. Maybe it's already there.
Every drugstore in America carries products that promise effortless weight loss. Fat burners, fat flushers, fat dissolvers, fat melters -- take your pick. Some of the products are practically household names thanks to massive advertising campaigns. Lipozene, a supplement containing the natural fiber glucomannan, has become a dominant presence on basic cable.
The glucomannan in Lipozene comes from the root of the Asian konjac plant or "elephant yam." Like other water-soluble fibers, glucomannan mixes with water to form an indigestible gel that could, in theory, create a feeling of fullness and blunt a person's appetite.
Incidentally, Lipozene's parent company -- which goes by the lofty name the Obesity Research Institute -- has gone down the glucomannan road before. The fiber was the active ingredient in two now-defunct products, Propolene and FiberThin.
Ads for Lipozene encourage viewers to order the product over the phone or online, but it's also available at drugstores. Either way, expect to pay about $30 for 60 capsules that each contain 750 milligrams of glucomannan. Users are instructed to take up to two capsules before a meal three times a day. At that rate, a one-month supply would cost about $90. Other companies -- including Nature's Way -- sell similar glucomannan supplements for about one-third the price.
The claims: According to the television ad, Lipozene is a "weight-loss breakthrough" that will help users shed pounds even if they don't exercise or change their diet. In the words of the pitchwoman, "It's so easy. Just take Lipozene. That's it." The ad claims that Lipozene's fat-reducing power was "clinically proven" in a "recent major university double-blind study." Fine print at the bottom of the screen says that subjects lost an average of 3.86 pounds over eight weeks. Viewers aren't told the name of the university, but they are assured that "78% of each pound lost was pure body fat."
The bottom line: There's simply no good evidence that the small doses of glucomannan offered by Lipozene could lead to significant weight loss, says Vladimir Vuksan, a professor of nutritional sciences at the University of Toronto.
Vuksan, who has been studying glucomannan and other nutritional fibers for the last two decades, says the active ingredient in Lipozene really can curb appetite -- at least a little. More so than other fibers, glucomannan forms an especially thick, viscous paste in the digestive system. Considered safe in small amounts, it's Food and Drug Administration-approved as a commercial thickening agent but not as a weight-loss supplement.
Vuksan estimates that it would take 20 to 30 grams of glucomannan each day to achieve substantial weight loss, enough to cause severe diarrhea and other gastrointestinal distress. Or, as Vuksan puts it, "your gut would explode."
A search of a medical database found no studies of Lipozene. There were also no glucomannan studies that matched the findings touted in the Lipozene television ad. The Obesity Research Institute did not return repeated calls seeking a clarification.
A small Norwegian study published in the journal Medical Science Monitor in 2005 found that overweight subjects taking glucomannan supplements lost an average of 8.6 pounds over five weeks, but they also stuck to a skimpy diet of 1,200 calories each day.
The mysterious Lipozene study aside, there's not much ongoing interest in glucomannan research, says Roger Clemens, an adjunct professor of pharmacology and pharmaceutical sciences at USC. "Glucomannan is generally passe in the medical and scientific communities."
Clemens says no single fiber can dramatically reduce weight, but he encourages dieters and everyone else to aim for 20 to 35 grams of fiber each day from a variety of sources.
The legal history of Lipozene's parent company doesn't inspire confidence. In 2005, the Obesity Research Institute agreed in a settlement to refund $1.5 million to customers after the Federal Trade Commission charged that ads for its glucomannan supplements Propolene and FiberThin were false and misleading. Among other things, ads for these products promised dramatic weight loss -- more than 2 pounds a week -- without diet or exercise.
Of course, there's no shortage of other supplements touted as weight-loss aids. Do any of them deliver? To get the Healthy Skeptic's take on a second -- conjugated linoleic acid, or CLA -- go to latimes.com/skeptic, where you can also read other past columns.
Is there a consumer product you'd like the Healthy Skeptic to examine? E-mail the details to firstname.lastname@example.org.