Nothing will completely stop catabolism, but glutamine will certainly help in that endeavor. I am a huge believer in the effects of glutamine, especially in amounts of 20 grams or more per day. It is my favorite supplement in fact.
As for HMB, it doesn't seem to do much unless you are on a very low calorie diet, like before a competition. It also doesn't seem to be of much use unless taken in amounts of 5 grams per day or more. Basically, don't waste your money on it unless you are entering a competition, and on a very low cal, low carb diet.