DEAR DR. ROACH: I am looking for advice on diet pills. I have tried everything. I eat well, go to the gym and walk, but my meniscus problem limits my walking speed. Since menopause, I have gained 30 pounds. I am sure there is something out there that will kick-start my metabolism. I am so depressed, and my doctor has no sympathy. -- A.R.
ANSWER: Difficulty losing excess weight is one of the greatest public health problems in industrial countries, and I'm not going to solve it here, but I'll try to discuss principles of drug treatment for weight.