They aren't compatible. Alli stops you absorbing fat but it does so by giving you the oily s**ts if you do eat fat... and whereas SW is a low fat eating plan generally, there are some healthy fats like oily fish, nuts, seeds and cheese/dairy which are supposed to be eaten on it. And then you have your Syns which allow you some treats which aren't on the SW plan (like when you really need a portion of real chips and nothing else will do) and you won't be able to have those on Alli. And the whole point of the Syns is so you aren't depriving yourself, don't feel starved and can stick to plan in the long term.

My verdict? Do SW according to the book and stay away from the pills - you could put the cost of the pills towards a gym membership if you want to accellerate your weight loss! (Alli is about £50 a month if I remember rightly.)

There's also the fact that on this forum people are against slimming drugs generally, and specifically to Alli, it hasn't been on the market long enough to know what the side effects of taking it without doctor's supervision are yet.

I may be able to help.  I lost 3 stones on slimming world in 3 months whilst taking a prescription drug called Orlistat or also known as xenical.  The reason I bring this up is because orlistat is the exact same drug as alli (according to my doctor).  The only difference is xenical is for people in the obese category and must be prescribed by a doctor.  Alli can be bought over the counter if you are in the overweight category.

Xenical is much more effective than alli, and allows 30% of dietry fat to pass through the gut undigested.   If you think you are obese (with a BMI over 30, you can check this online) you can get Xenical from the doc and its MUCH cheaper and more effective than alli.  Its only about £5 for a month’s supply.  However if you are not obese and just overweight you’ll have to continue to buy alli (which i’ve heard is expensive).

Both drugs have the same side effects.  The main one is “oily farts” which is like an orange oily substance that leaks out your bottom when you break wind.  This sounds disgusting however, it shouldn’t bother u if u take them sensibly.  For example, if u eat something that u know doesn’t contain a lot of fat then you will be fine.  If you are overindulging or having a “treat” then simply don’t take one, and you wont suffer from this side effect.  I was on xenical for a long time and it only ever happened to me a couple of times....but that’s because I ate pizza and took a pill.  So i was asking for it!

So, if Xenical worked greatly for me with Slimming World then I’m sure Alli will work for others, as any drug that stops fat going to your hips is great on any diet.  Because slimming world is a low fat diet, which if you follow correctly, you will not be bothered with the pre mentioned side effect.  If you are having a treat after saving up syns, just don’t take a pill with your meal!