Weight loss always comes down to a calorie deficit. No matter if it’s through surgery, medication, or behavior change this is always the mechanism for successful weight loss. Supplements offer a tempting solution for those that feel like they need that extra boost to achieve that calorie deficit. As a registered dietitian, my opinion on weight loss supplements has changed over time in being more supportive of the short-term use of them while you work on sustainable behavior change. However, supplements that block the absorption of certain macronutrients will not receive my support because our bodies need all of the macronutrients for vital functions in the body. Alli is an FDA-approved performs in this way- by blocking fat absorption into the body. Let’s explore how this supplement performs and the consequences of long-term use:

Ingredients: The active ingredient is orlistat which binds to the enzyme lipase, inhibiting the absorption of fat 

Alli works by blocking an enzyme (something that breaks up food in your body) from breaking down fat in the digestive system. Therefore, you simply aren’t absorbing and processing all of the calories that you may be consuming. The idea is that you don’t have to change too much about what you’re eating and that this medication will do the work to decrease fat gain internally. However, the manufacturers instruct consumers to only eat 15g fat per meal in order for the supplement to work properly which is actually a pretty low amount. For reference, 1 tablespoon of olive oil is 14g fat. So unless you’re eating a salad with no cheese and avocado this may be difficult. Plus eating an overall low fat diet will ultimately limit calories anyway, so you may not even need the supplement to see results. Alli is also intended to be taken within 1 hour of eating you meals and is recommended only for those with a BMI over 25. Further recommendations include adhering to an exercise routine and eating an overall healthy diet. Which also will likely cause weight loss without even needing to take the pill. 

Because this supplement helps you to lose weight through means of altering your gastrointestinal function, side effects can include oily stools (because the fat you eat has to come out somewhere), gas, bloating, and diarrhea. And it should be noted that this is what happens if you eat above that 15 g fat guideline. We all need to intake some fats because vitamins A, D, E, and K are all fat soluble, meaning they are absorbed through the fat that you eat. Therefore, eating too little fat could become deficient in these needed nutrients.  

Alli is an older weight loss supplement, becoming available in 2007. Because of this, we have some significant research to show the efficacy of the medication. Research suggests that this supplement does actually help with weight loss. When comparing it to those who aren’t on the medication, the group taking Alli loses about twice as much weight in 1 year. However, another study showed that the group taking Alli had increased gastrointestinal distress and no significant weight loss. So in other words, you may lose weight or you may not. 

Overall thoughts

As a Registered Dietitian, I would not recommend this supplement because it seems like the changes that you need to make to be compliant will help with weight loss anyway. Plus the extra weight loss that you will have from taking Alli happens through not absorbing all of the fat you eat. And you need fat! Healthy fats from plants and fish actually help with anti-inflammation, which helps you feel better and lose weight. 

If you are trying to lose weight, I would recommend trying the same lifestyle changes that this supplement recommends- an overall healthy lifestyle with a calorie deficit and an exercise regimen. This is cheaper, healthier, and likely more sustainable.

To start your healthy weight loss journey today, learn how to track what you eat! This can help you to make sustainable changes in what you’re eating so you don’t have to keep learning new and complicated diets. Watch our tutorial to get started today.