Users of Alli, the first weight-loss drug approved for sale over-the-counter in the United States, are finding what they likely suspected all along: pills are no magic substitute for diet and exercise.

Yet as Americans engage in the New Year's tradition of resolving to shed pounds, the market for diet aids is expected to remain firm, even as the economy is mired in recession.

Americans spend $30 billion a year on weight-loss products and services, and two-thirds of the population is overweight or obese.

GlaxoSmithKline's Alli, a lower-strength version of Roche's prescription-only Xenical, created' a stir when it was approved 18 months ago.

Since then, it has become known for its unpleasant side effects, including incontinence, diarrhea and flatulence with "oily spotting."    
"It works to inhibit absorption of fat from our diet. Therefore the fat comes out in the stool, causing diarrhea, which patients don't like much," said Shirley TerMolen, a Chicago internist.

Because the side effects result from eating too much fat, TerMolen noted that some of her colleagues use the drug to help patients modify their behaviour.

TerMolen said she has prescribed the drug but has not seen a lot of success. "For most people, they're just looking for a shortcut instead of just eating better and exercising," she said.

Donald Hensrud, a weight management specialist at Mayo Clinic, called the gastrointestinal side effects overstated. But, he added, the intended effect "is also overrated."    

"People who took the drug lost only 4 more pounds (1.8 kg) than the placebo group after a year. People have to ask themselves whether the expense of this medicine is worth a few extra pounds," Hensrud said.

A 30-day supply of Alli costs $60.

People who took Xenical, the prescription strength version, lost an average of 5 to 7 additional pounds (2.2 to 3.2 kg) after a year compared with those who took a placebo.

Still, experts say weight loss of 5 percent to 10 percent is a worthy goal and a point where health improves.

Meanwhile, Alastair Wood, who chaired the Food and Drug Administration advisory panel that reviewed Alli in 2006, said he's not convinced the drug is being used by the people who would benefit most. In some cases, it is abused by people with eating disorders, he said.

"It's a juxtaposition of an epidemic of obesity with the hope and expectation that we can treat it pharmaceutically," said Wood.

Glaxo stresses Alli is not a "miracle pill" and that patients should adhere to a low-calorie, low-fat diet and engage in regular exercise.

Roger Scarlett-Smith, the company's president of consumer healthcare in North America, said 5 million people have tried it so far and he expects that number to ramp up in the first quarter, a strong season for weight-loss products.

It was approved for over-the-counter sale in Europe this week.

The history of weight-loss drugs has been fraught with disappointments. One of the most high-profile was Fen-phen, a cocktail of fenfluramine and phentermine, which was taken off the market in 1997 after it was linked to valvular disease.

Also in 1997, the FDA approved Abbott Laboratories' Meridia, or sibutramine, which blocks chemicals in the brain involved in regulating appetite. The drug was linked to hypertension.

Sanofi-Aventis sells Acomplia, or rimonabant, in Europe, but not in the United States. FDA rejected it in 2007 on concerns it causes neurological and psychiatric problems.

There are few promising treatments in the pipeline at a time when obesity is emerging as one of the biggest health crises facing the developed world.

Earlier this month, Orexigen Therapeutics unveiled results from a late-stage trial of its experimental drug Contrave, which fell short of the bar set by US regulators.

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