I does what it says on the tin. It works by preventing absorption of fats from the intestine.They run right through you
You have to eat as little fat as possible or you end up with nasty oily diarrhoea.
It doesn't work with a low carb approach.
It can be effective. I suspect that some of that is by making peeople eat low fat, to avoid the side effects.
It certainly wouldn't suit me
Hana