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 nutrients as well.
What do you think? Share this post or join in or start the discussion below!


  1. So tired of reading reviews of dieting supplements by people who are 20 years old and/or 150 lbs.
    Alli works. For what it’s meant to do. It blocks fat. If you are on a super low fat diet, it will do nothing. If you on a super high fat diet, you’re going to be crapping your guts out. It’s very hard to go both low carb and low fat and have good food. Alli allows you to be a little more reasonable with your diet, and know some of the fat won’t be absorbed. I was 38 years old and 300 lbs. in July. I lost 40 pounds by hitting the gym every morning. But I was stuck at 260. For the past week now I’m doing more cardio, taking a fat burner, and taking Alli, and the weight is dropping fast. I’m down to 250, and I plan to be under 200 by July.

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  2. I tried Alli for about five week, I lost 10 lbs, but I started geting severe neck pains, my face was swelling on one side and the last thing my lips swell up likea catfish. I called my doctor he said I was alergic to Orlistat which is a main ingredient in this product. I was advised to discontinue these at once. I have been off it tow weeks and my body id back to normal.

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  3. Ive been on Alli for 15 days and have lost 4 lbs.

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  4. I have used alli in the past and lost 5-10 pounds in around a couple weeks to a month. The worst time of weight gain is when you quit smoking, and again I have gained weight.

    When you quit smoking, you no longer substitute meals for smoke breaks, your metabolism goes to crap, and your hunger skyrockets.

    I was working out and eating right a month prior to quitting. Dieting and exercising 2 months now, and having quit smoking a month, I have gained 5-10 pounds. I am going to use my friend alli to burn this fat back off for a kick start back into my plan.

    Just know, that once I went to hooters and took an alli before. Like the other comments, yes, you do pee your butt. Watch what you eat. If you are going to use alli for a coushion when you cheat on the diet, be prepared. Never try to rip a quiet one, always go to the bathroom, or else you are going to have to go home and shower and change and buy more spray and wash.

    Last but not least, as much as I discourage people from going there, I find alli is the cheapest at walmart.

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  5. even if you do eat “properly” with this pill, i still pee out my butt. this is BS!! i get oily spots on my undies!! ewwwwwwwww

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  6. When will Alli be back on the selves? I miss it and have lost 15 pounds.

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  7. When will alli be on the shelves again

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  8. Alli worked for me…no longer can locate in my area stores. Where can I purchase Alli again? Thank you!

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