I have never heard of any dog starving itself to death; unless of course, there is a very bad medical problem. Your dog doesn't sound like that. He needs time to adjust, as another has said. Since you mentioned having other dogs, you might already be aware of the amount of exercise a PittBull needs!
They were originally bred to chase bulls, at bull fights, and in pastures, getting to go where the owners wanted them! They need a lot of exercise. If they don't get it, like brisk 45 min. walks every day, they will turn into being bored, and become very aggressive.
I apologize if you already know this, and here is some more information on dogs:
I highly recommend a video by Ceaser Millan, a Professional Dog Behaviorist. He rehabilitates dogs, and trains people.
He has his own TV program, the Dog Whisperer, on the NGEO (National Geographic) channel, on Friday nights mainly, but also comes on some other days. This video is available from: http://www.dogpsychologycenter.com/
I also ordered his new book, "Ceaser's Way", from Walmart online, around $15 US, and it's very good!
There are other good videos available on the web, but this one is really worth your attention.
There is absolutely nothing wrong with Pitt Bulls, providing the owner knows how to train them, and how to give them the exercise they need, on a daily basis. They have been banned by some State and local ordinances, simply because the owners would not take the time to train them, and be aware of what they should do. I do wish you the best, and good luck.