When you purge, how do you know how many calories you've gotten rid of? I cant imagine it being very much to be fair, unless you got rid of every single thing you ate (which sounds impossible to me)

It is very difficult to say- as soon after consumption..your body soon starts to absord calories....u may be able to tell how much food you have pruged back up, but the kcals may already have been absorbed after 15 mins (well, some of them, im afraid)

i've heard that you consume 75% of the calories you eat no matter how quickly you throw them up. that is why a lot of the times bulimics don't weigh 95 pounds, etc. adn their faces are often swollen. i don't know if it's true, but it's what i've heard....

I think it depends a lot on how long you wait before you throw up. I do it straight straight after to get as much as I can out of my system, but in recovery for bulimia they try and get you to sit with someone for an hour or so after you've eaten before you purge. I guess this is a way of getting your body to absorb more calories? But I don't really know to be honest.