"i have been on orlistat for 2 weeks and already i have lost 10 lbs! it takes a few days to know what you can and can&#039;t have...trust me you will too! ha! the only &#039;side effect&#039; i&#039;ve had was loose stools at quite short notice (but enough notice to get to the bathroom) and this was only because i had a small slice of birthday cake. otherwise i haven&#039;t experienced any grim &#039;side effects&#039; you definitely have to change your eating habits though. looking forwards to my next lot off my doctor."