Recently I got a frantic letter from Barbara, who lives in Florida. It seems that her teenage son has taken up bodybuilding and her husband is adhering rigidly to the Atkins diet, both of which are protein heavy. Barb got through the first week with a major case of mixed emotions: Her husband lost 7 pounds, her son gained 4—and her food bill doubled! Can Barb keep her food costs down while still supporting her family’s eating choices? I know she can. Special diets don’t have to be budget-busters. In the same way her son and husband are adjusting their way of eating, Barb must adjust the way she shops. Don’t Pay Full Price for Protein Tuna, chicken breasts, and lean beef cuts are always on sale somewhere. If you don’t want to store-hop, you can always find some cut of meat, fish, and poultry on sale in your favorite …