Forget carbs and fats; wishful thinking about what it really takes to lose weight for the long haul is the staple of the American diet. In fact, it should be at the top of the food pyramid, because when it comes to myths about dieting, Americans seem willing to swallow just about anything.

Or at least one of America’s biggest drug companies thinks so. In fact, GlaxoSmithKline (GSK) Consumer Healthcare North America thinks Americans will spend about $1.5 billion each year buying the myth that diet pills really help people lose weight and keep the pounds off. It has asked the federal Food and Drug Administration to approve over-the-counter (OTC) sales of its prescription weight loss drug Xenical, and expects Americans will buy $1.5 billion of the OTC version annually even though Xenical works so poorly that most American physicians do not prescribe it for their overweight patients.

Unfortunately, it would be a stretch for the FDA to prevent all of us from spending our money on a diet drug that barely works, so an FDA advisory committee recommended last week that the FDA approve GSK’s request. I am betting my bikini GSK soon gets the final approval it wants from the FDA, and the company expects to start selling Xenical this summer as the OTC drug “Alli.”

Part of the reason GSK believes it has an OTC winner is that Xenical/Alli is a so-called “fat blocker” drug; it works by blocking the body’s absorption of some of the fat eaten in a typical meal. How cool is that? It can block absorption of 150 to 200 fat calories per meal, according to GSK, and sounds like the miracle weight-loss drug we have been weighting for.

The siren song of Xenical’s fat-blocker weight-loss message sounds so good GSK is hoping we will not hear the sour notes sung by scientific data showing it works poorly over the long haul. In studies done by its manufacturer, patients taking Xenical for a year lost about 11 pounds, but only about six more pounds than patients taking no weight-loss pill. Worse, when those taking Xenical stopped the pill, they regained about half of the weight they had lost. And worse still, its more unpleasant side effects include excessive flatulence, oily stools and that party conversation favorite, fecal incontinence.

Let’s sum up – at a cost of $1,200 a year and side effects in more than one-third of patients, Xenical produced about five pounds of permanent weight loss. Other than that it is a great drug. As miracles go, however, you were better off spending your $1,200 on a good pair of sneakers, a treadmill and a trip to the Shrine of Turin.

GSK’s priority is its bottom line, not your bottom line, however, and it is undaunted by Xenical’s lack of substantial benefit for users. American doctors wrote only one million Xenical prescriptions in 2004, but GSK knows it can do better by getting medical professionals out of the loop between you and its fat blocker. Once the pill goes OTC, GSK estimates that 5 million to 6 million Americans will buy Alli each year, at a cost of about $12 to $25 a month, all hoping for weight-loss help.

The name Alli sounds like hope in a pill. If “Alli” is pronounced “ally” (as in a friend in a cause), it sounds like real help in the battle to lose weight. If pronounced “Allie” (as in a woman’s name) it sounds like a sleek TV star that a woman buying the pill would want to look like. GSK figures a fat blocker with a great name and millions in advertising behind it a sure winner.

And sadly, GSK is probably right; Alli by any pronunciation is a safe bet on GSK’s part. After all, Americans spend billions on other would-be dietary miracles each year, and GSK knows that with good marketing of an “FDA-approved” fat blocker it can get a piece of that rich pie. Drug stores, diet programs, supermarkets, magazines and the Internet annually sell us billions of dollars worth of miracle diet pills that promise a thinner you, most with even slimmer evidence of long-term safety and effectiveness behind them than Xenical/Alli.

If you search the Internet for “fat-blocking medicines,” for example, you will find more ads for “fat blockers,” “fat burners” and “Max Fat Burners” than you could swallow in a lifetime of dieting. You can buy diet pills such as “Metabo-SpeedXXX” (designed to appeal to the myth that weight gain is caused by slow metabolism), scam creams that “melt the fat away,” creams that “melt cellulite” and probably pills that claim they can melt your pounds away just by you sitting there looking at them.

Would that it were so, but all of the noise is just the sound of wasted money being sucked out of our wallets. There are no miracle pills, and nothing that works to keep the pounds off over the long haul except a good diet and regular exercise (and gastric bypass surgery for some of those who are extremely overweight). The answer is in pounding along pavement, not pounding down pills.

If all of this does not convince you to keep your money and let GSK keep its Alli, then buy just one and consider this use of Alli (or any other diet pill); when tempted to eat too much, take your diet pill and hold it firmly between your lips until the urge to eat more passes. Held there it will do a better job of blocking fat and keeping the weight off than any diet pill you swallow day after day, dollar after dollar.

Erik Steele, D.O., a physician in Bangor, is chief medical officer of Eastern Maine Healthcare Systems and is on the staff of several hospital emergency rooms in the region.