As a top-selling over-the-counter drug, Alli (Orlistat) presents incredibly well. “The only FDA approved, over-the-counter weight loss aid!” So what does it actually do?
Orlistat gums up the breakdown of fats in the gut, leading to less fat absorption and more fat excretion. Think of it as the “eat your ice cream and don’t absorb it” pill. All that fat can cause problems at the other end, but supposedly not on the hips.
So, why is Alli Amazon’s top weight-loss seller? It’s the only FDA approved drug for weight-loss. In clinical trials it helped people lose weight and there’s nothing else available. But it’s not the only FDA approved drug for weight loss (although it gives that impression): “At present there are three drugs (orlistat, phentermine/topiramate and lorcaserin) approved for long-term use and four sympathomimetic drugs approved by the US FDA for short-term treatment of obesity.” (cite here) It’s the only over-the-counter version, because almost none of it is absorbed. That still doesn’t mean it can’t affect your medication, and may block absorption of that as well. 
If you look at the prescription version of Orlistat, Alli’s bigger brother Xenical, the studies look very official, if small. (Here) It makes Xenical look really useful for minor weight loss, and so Alli should be too. Sure, it’s much ado about very little, but every little bit helps.
But it really comes down to the amount of weight people think they are going to lose with Alli versus without Alli. And that’s what really makes the difference. So let’s pool all the clinical data in one review:
“Behavioural interventions focusing on both food intake and physical activity resulted in an average difference of -1.56 kg (95% confidence interval -2.27 to -0.86 kg; 25 comparisons, 2949 participants) in weight regain compared with controls at 12 months. Orlistat combined with behavioural interventions resulted in a -1.80 kg (-2.54 to -1.06; eight comparisons, 1738 participants) difference compared with placebo at 12 months. All orlistat studies reported higher frequencies of adverse gastrointestinal events in the experimental compared with placebo control groups. A dose-response relation for orlistat treatment was found, with 120 mg doses three times a day leading to greater weight loss maintenance (-2.34 kg, -3.03 to -1.65) compared with 60 mg and 30 mg three times a day (-0.70 kg, 95% confidence interval -1.92 to 0.52), P=0.02.” (Review here)
There you have it. Alli helped people lose more weight, a whopping 0.24 kg (8.47 ounces or roughly half a pound) over not taking it. And a greater increase in weight loss the more you took. Sign me up for a couple of bottles (and an extra jumbo pack of toilet paper).
But we no longer have just the clinical studies to look at now. Alli has been released on the general population, and we have big data on how well it has fared. In a study of 100,000 English, Alli resulted in: (trumpets please) about two pounds of weight loss for the first four months. Afterward, they regained the weight. (Study here). The difference? This was in the real world, not in a monitored group of patients who continued to be part of a funded study. In the real world, people lose focus, and when they are getting something over-the-counter instead of as a prescription they can lose focus faster. No one monitored their weight loss, so it disappeared.
Alternative Holistic Health Answers 