My boyfriend is slowly losing weight and we would like help in selecting a weight gain formula from (GNC?). He is 47 and healthy, plus he eats good. There are so many different formulas out there to choose from. Does anyone have names of specific ones with the pros and cons of each type, or any other suggestions of what we could do to help him gain weight? He has a normal exercise level so more excercise will make him more fit, but not necessarily gain weight.