Alli side effects are downplayed by the drug company that makes it and by websites that sell it. You can expect that when any drug blocks the action of a crucial digestive enzyme, which is what Alli does, nasty consequences will follow. Expected weight loss isn’t even all that good.

Alli Official Website FAQs

Alli is an over-the-counter drug approved by the FDA for weight loss. It was approved for OTC as a low-dose version of the prescription drug sold as Xenical or Orlistat, made by GlaxoSmithKline. The official website, MyAlli.com, is owned by SmithKline Beecham Ltd. of the United Kingdom. The FAQs section states the following (with some corrections in punctuation):

Alli works in the digestive tract and is minimally absorbed in the blood. Alli’s active ingredient, orlistat, works by inhibiting fat absorption. This means that around 25% of consumed fat passes through the digestive system and is naturally excreted by the body. Since the calories associated with this unabsorbed fat are not used (1 gram of fat=9 calories), the number of calories that enter your system is reduced. Orlistat doesn’t limit the absorption of calories from protein or carbohydrate. So, if you replace calories from fat by eating carbs, you will not get the benefits of alli and will lose less weight. Therefore, it is important to stick to your calorie and fat target by eating foods that are naturally low in both calories and fat.

And from Orlistat on Wikipedia:

Mechanism of action: Orlistat works by inhibiting gastric and pancreatic lipases, the enzymes that break down triglycerides in the intestine. When lipase activity is blocked, triglycerides from the diet are not hydrolyzed into absorbable free fatty acids, and are excreted undigested instead.

Comment: Alli blocks the action of essential dietary enzymes. Your available dietary calories will be reduced when you are unable to metabolize fat. You have to make up for this reduction, since your body has a certain level of demand for energy according to your Basal Metabolic Rate. Using Alli amounts to reduced-calorie dieting, unless you make up for your metabolic needs by eating more, which you will have to do. If you add carbs, though, you will undermine any results from taking Alli.

You could, therefore, duplicate your weight loss results from treatment with Alli by just eating less. Alli is, at best, unnecessary. At worst? Read on.

Alli Side Effects – Stay Close to Your Bathroom

Drug companies call these treatment effects. I suggest the you keep in mind the difference between targeted treatment effects – i.e., weight loss – vs. non-targeted treatment effects. The latter are side effects, regardless of what the company calls them.

Side effects supposedly occur when taking Alli with a meal that includes more than 15 grams of fat from all sources. What does that mean? If you used calories as a benchmark, this would be 135 calories from fat in one meal. Assuming somewhere around a 2,000 calorie per day diet, dividing meals evenly (i.e., 670 calories each), you should not exceed 20 percent of your caloric intake per meal in fat.

In reality, lunch and dinner are probably larger than 670 calories. If you had an 800 calorie dinner, then the maximum would be about 17 percent allowed as fat. In simple terms, you would not be able to have fries with that burger after taking Alli.

Now back to those ‘treatment effects’:

alli works by blocking the absorption of one-fourth of the fat in the foods you eat. This undigested fat passes through the body naturally and it is not harmful. In fact, you may recognize it in the toilet as something that looks like the oil on top of a pizza.

They forgot to mention flatulence, abdominal cramping, diarrhea, and anal leakage. Small oversight, eh?

What Are The Chances?

Here is what Wikipedia has to say, which is not on the company website (the highlights are mine):

According to Roche, side effects are most severe when beginning therapy and may decrease in frequency with time;this is supported by the results of the XENDOS study, which found that only 36% of people had gastrointestinal adverse effects during their fourth year of taking orlistat, whereas 91% of study subjects had experienced at least one GI-related side effect during the first year of treatment. It has also been suggested that the decrease in side effects over time may be associated with long-term compliance with a low-fat diet.

If this is correct, 9 out of 10 people can expect to have problems during the first year of treatment! WOW! And that goes WAY down to 36 percent of users having ‘adverse effects’ through the fourth year! Double WOW!

In other words, you can expect trouble.

Additional Problems Are Deadly

Less common side effects may also occur. These are enough to scare the beejeezus out of anyone, regardless of what the incidence is (from Wikipedia; again, highlights are mine):

On May 26, 2010, the U.S. Food and Drug Administration (FDA) has approved a revised label for Xenical to include new safety information about cases of severe liver injury that have been reported rarely with the use of this medication.

An analysis of over 900 orlistat users in Ontario showed that their rate of acute kidney injury was more than triple that of non-users. The putative mechanism for this effect is postulated to be excessive oxalate absorption from the gut and its subsequent deposition in the kidney, with excessive oxalate absorption being a known consequence of fat malabsorption.

The phrase ‘excessive oxalate absorption from the gut and its subsequent deposition in the kidney’ is what leads to kidney stones and subsequent kidney injury.

And What Do You Get Out of Alli?

Let’s not mince words. Here is a summary of research results on Orlistat, which is more potent than Alli:

Orlistat is used for the treatment of obesity. The amount of weight loss achieved with orlistat varies. In one-year clinical trials, between 35.5% and 54.8% of subjects achieved a 5% or greater decrease in body mass, although not all of this mass was necessarily fat. Between 16.4% and 24.8% achieved at least a 10% decrease in body mass. After orlistat was stopped, a significant number of subjects regained weight—up to 35% of the weight they had lost.

In the best-case scenario, you have half a chance or so (i.e., up to 54.8 percent) of achieving a 5 percent decrease in body mass. This would mean that, if you weight 200 lbs to begin with, a 5 percent loss would be 10 lbs. This is over several months to a few years. And you would probably gain more than a third (35 percent) of that back.

Any result that has been obtained for Orlistat will be more than what you can expect from Alli, since Alli is the low-dose version of Orlistat.

Now that you are armed with a few facts, you can answer the question for yourself:

Is Alli worth it?

You decide.

Updating Alli side effects,

Dr. D