The only treatment that is going to benefit the person suffering, is
one that deals directly with the underlying causes. For this reason,
many treatments simply suppress a few symptoms. They do not effect
cure. Measures of success have nothing to do with weight. Locking
someone away and preventing them from purging is not a solution. If
anything, it contributes to anxiety.
You can find a number of useful techniques to help at http://www.bulimiagirls.com