I am thinking about my brother a lot these days. He is 22 years old and has been a drug user for almost 3 years. He started with Ecstasy pills on rave parties and now he uses crack, I guess because it is cheap. He left our home while he was just 18 and worked various jobs to survive. Now he is dealing with drugs and I don't know what will happen to him. Last time we met, he looked so skinny, can crack affect the lining of the stomach? I mean, I know that there are much worse symptoms but he lost so much weight!
Weight loss happens not because of stomach problems (even though this might happen), but because of his mental state. Crack can make him lose interest in well, almost everything, including loss of appetite. If you worry for him, get him to the institution that deals with these kinds of problems. I don't think that you will be able to make him leave crack just by talking. He needs professional help.