OP, I have some similar issues, although I'm guessing my body chemistry is a bit different than yours.First of all, I'm female. I'm about 120 lbs now (only about 5'2, so short also), and when I was in highschool I was about 170 lbs (I'm in my early 20s now). Anxiety tends to make me not eat. Due to some life circumstances a few years ago, I dropped 30 lbs all at once, and the other 20 at some point before it. Since this weight loss, my appetite sucks. And I'm blaming pot for it --- I normally don't feel hungry unless I smoke first. When I'm at home visiting family I have a very hard time eating during the day, but I generally have a hard time eating when I'm anxious, stoned or not.
So, what I've been doing now is trying to force myself to eat BEFORE I smoke. Like, I won't allow myself to smoke pot if I haven't eaten yet that day (unless I have my period which causes some ungodly nausea). After sort of retraining myself to do this for a while, I seem to be able to eat more and more food without the help of pot...I've been working on it for quite some time though, and after getting so used to pot helping my appetite out, it's a little strange. Plus, I used to be fat so I'm guessing I also need less food now than I used to as well. On days where I'm very anxious, or for some reason have no access to pot/benzos (if I take a benzo I'll get hungry when it kicks in, since the basis of my loss of appetite is an anxiety issue I think) I will try to have some chocolate milk, or carnation instant breakfast --- something along the lines of the protein shakes others have suggested. That way, I'm still getting some calories in, and your stomach won't make those odd sounds if you can manage to get something thicker than water down. I've been told that if you've been crying/just very upset, it's okay to go a couple days with almost no food, but just make sure you are staying hydrated at all times...since the body can survive without food but not without water.
So, to summarize --- start trying to eat BEFORE you smoke, and not letting yourself eat after you do. Also, any of those high calorie and nutrient shakes will help your body get what it needs. As I said, our chemistry is a bit different since I'm female and previously was overweight, but I do think weed is causing the problem (been using it daily for about 7-8 yrs now, so I barely remember a time without it). Since weed actually helps my anxiety, I think anxiety could have something to do with it as well.