Alli Information: Over The Counter Fat Blocking Pill


The diet pill Alli is Glaxo Smith Kline’s “de-tuned” version of the popular diet drug Xenical. Alli contains approximately 50% of the Orlistat present in the Xenical prescription pill. It’s available “over the counter” without a prescription, meaning consumers have complete and easy access to what is arguably a prescription drug.

How does Alli work?

Like Xenical, Alli works in the gut to reduce the amount of fat your body absorbs from a meal. It inhibits the action of the enzyme lipase which is necessary for the absorption of fats in the small intestine and stomach.

Undigested fats are not absorbed and therefore do not add to the caloric balance of any particular meal. This may result in a reduced caloric intake, and therefore, weight loss.

Of course, Alli only blocks the absorption of fat. If you’re consuming low fat meals, you don’t need Alli, Xenical or Orlistat. It won’t do anything to inhibit the absorption of “carbohydrate” calories.

It’s important to make note of this as there’s been a continuing trend of a reduced fat intake over the last few decades, while carbohydrate intake has continued to increase.

In other words, if most of your “bad” calories come from sweets, and not fats, Alli is not for you.

The good news is that like Xenical, very little if any Alli actually enters the bloodstream. It works in the gut and the small intestine. That means it won’t effect the central nervous system like most diet pills.

The bad news is that neither Alli or Xenical differentiate between blocking the “bad” saturated fats and good, cholesterol-lowering poly and monounsaturated fats. Both drugs also inhibit the absorption of fat soluble vitamins and beta-carotene making supplementation with a quality multi-vitamin necessary when using either Alli or Xenical.

What are the Alli side effects?


Prepare yourself for some unpleasantness. Because the fat in a meal does not get absorbed, it has to leave your body somehow — and that’s through the stool. When taken with a high fat meal, possible side effects include bloating, gas, “oily spotting,” diarrhea, and possibly, “anal leakage.” The best way to reduce these nasty side effects is to limit the amount of fat consumed in any meal — no more than 30% of any meal’s calories should come from fat.

It’s although worth noting that The Public Citizen’s Health Research Group (a non profit advocacy group) does not like Xenical, Alli, or Orlistat at all, claiming they can cause gallstones and pre-cancerous abnormalities. Click here for more information on Alli side effects! Additionally, the FDA is investigating Alli for possible liver damage.

What about Alli’s interactions with other drugs? Alli interacts with both warfarin (it increases its effect) and the antibiotic cyclosporine (it decreases its effect).

Bottom line?

Although available over the counter, Alli is, for all intents and purposes, a drug. It should be treated with respect and I would not recommend you take it without first consulting with your physician — especially if you are taking any other medication.

If you’d like information on Xenical, the full dose, prescription version of Alli, you can read the full review here!

Alli Summary
  • Probably one of the best-researched over-the-counter weight loss pills on the market.
  • Works by a known mechanism.
  • Company provides plenty of information on how to use the product safely and effectively.
  • Potential for unpleasant and embarrassing side effects.
  • Pointless if you’re already eating a low-fat diet.
  • Not cheap.
  • May interfere with absorption of healthy fats/fat-soluble nutrientsĀ as well.


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