This TOC diet drug, to be sold under the trade name of Alli, has the same ingredient as the prescription diet drug xenical, which was approved in 1999. Both contain orlistat.   Both are made by Roche Holding AG and marketed or to be marketed by GlaxoSmithKline PLC.

The difference is, Alli contains 60 mg orilistat per capsule and is indicated for overweight adults while xenical contains 120 mg per capsule and is for obese adults.

Both diet drugs work only if patients follow a comprehensive program designed to boost the weight loss effect of orlistat.   In early trials, participants were offered advice on nutrition and exercise.

The way orlistat works to prevent weight gain or promote weight loss is to inhibit enzymes that would otherwise facilitate absorption of fat in the gastrointestinal duct. As reported, the drug can stop as much as 20 to 30 percent of dietary fat from being absorbed.

Because fat-soluble nutrients need fat as carrier to get into human body, the diet drug inevitably blocks absorption of fat-soluble vitamins such as vitamin D, K, E, and other fat soluble nutrients. For this reason, the consumers of orlistat are suggested to take a multivitamins at bedtime to compensate the loss of nutrients due to the use of the diet drug.

To have the maximum effect, along with orlistat, one needs to use a low fat diet with total calories reduced by 20 percent and do physical exercise as instructed in a 250-page users’ book which is given when the medication is purchased, according to news reports. This means that the dieters will do more than just popping pills three times a day with a glass of water.

Although the regimen including counting of calories is complicated, trial results indicate the weight loss resulting from the diet drug can be marginal, as Public Citizen, a not-for-profit organization that defends consumers’ interest calls it.

In early trials, two groups of men and women were instructed to use a low fat diet with total calories reduced by 20 percent and to do physical exercise. One group was assigned orlistat and the other a placebo.  

As a result, participants who were assigned orlistat experienced a loss of 5.7 pounds over a period of six months, 50 percent more than what those who were not on the drug did.

In the trials, the low fat diet might to play a more significant role than the diet pill in the loss of the 5.7 pounds.   Using a diet with total calories reduced by 20 percent means that one ate 400 calories less each day during the six month study.

In contrast, the magnitude of weight loss experienced by the subjects on orlistat amounted to loss of 110 calories per day for six months, which was not much as compared to the reduction of calories by using a low fat diet.

Although the loss of 5. 7 pounds in six months was not as much as desired, it still required much of other efforts including physical excise and using a low fat diet, meaning that using the diet drug was not easy.

Suppose that the dieters used a diet with calories reduced by 25 percent rather 20 percent as in the trials, those patients in trials would possibly have achieved the same effect without taking orlistat.

While the effect of orlistat is moderate or even marginal, it is pretty costly.  For a six-month program, one needs to spend $300 or more on the pill.  For one week, it costs $15 to 25.   The investment does not count the time spent as required by the comprehensive weight loss program.

The worse part is this: early studies showed the weight loss effect diminished and lost weight came back after use of the drug was discontinued. Those who want to keep the pounds off need to keep taking the pill. But that is not advisable because the long term adverse effects of this diet drug remain unknown.

Considering the fact that the drug prevents absorption of fat-soluble nutrients, potentially leading to malnutrition, it is unreasonable for one to continue the dieting regimen beyond six months.   What does that mean is, you may have to lose the regained weight again later.

The side-effects of using orlistat, prescription or TOC, include gas with discharge, oily discharge, increased number of bowel movements, oily spotting, oily or fatty stools, urgent need to have a bowel movement and inability to control bowel movements. About 50 percent of patients on the drug experienced some side-effects and seven percent lost bowel control.   For this reason, one may have to take another drug to get the side-effect under control.

The scariest thing is, mice treated with orlistat were found to develop precancerous lesions of the colon, which could cause colon cancer, according to Public Citizen, a not-for-profit organization that defends the interest of consumers. We just do not know if this side-effect would occur in humans.

While the weight loss caused by orlistat may be marginal, to lose 5.7 pounds with orlistat is not as easy as popping a pill a time, three times a day. Overall, using weight loss drug seems quite a task for many people, considering it only causes a modest weight loss.

Public Citizen calls the plans to market a non-prescription version a "dangerous mistake" because the benefit of the weight loss pill is “marginal” while the diet pill can have "bothersome adverse reactions."

Sidney M. Wolfe MD and Elizabeth Barbehenn, Ph.D., with Public Citizen's Health Research Group, on Jan. 23, 2006 testified before the FDA advisory committee raising their concerns based on certain facts little known to outsiders.

They said that, "The long-term effects of Orlistat on morbidity or mortality associated with obesity have not been established." Glaxo did not report earlier how the diet pill affects blood pressure and serum lipids, which are commonly associated with obesity.

"Although a statistically significant weight loss for Orlistat 60 mg compared to placebo is seen, there is no evidence presented that a modest, transient weight loss due to orlistat will afford any long term clinical benefit either through a change in behaviuor or a reduced risk of serious clinical disease manifest by being overweight," Wolfe and Barbehenn said in their testimony.

"Physicians are increasingly rejecting the prescribing of Orlistat (decrease from 2.6 million US prescriptions in f.y. 2000 to 1.0 million in f.y. 2004). It is clearly in GSK's (and partner Roche's) interest to seek OTC approval. Your committees need to reject this desperate attempt to revive this barely effective drug by an OTC switch."

A scientist affiliated with foodconsumer.org suggests that there are better ways than taking this drug to shed pounds. The most concerned is not that the pill does not cause bigger weight loss.  It is rather that this approach could harm one’s overall health.

Glaxo said in a statement that the company would make Alli, the TOC version of orlistat, available nationwide within six months.   It expects that 2 to 4 million Americans will buy the diet pill.