What do I need to do to help my elderly dog gain more weight... seems to be that the "normal" dog food isn't helping no matter the amount he is getting. He is a 9 year old American Bulldog, so getting up there for his breed. I remember somewhere it is either a higher protein or a higher fat will help get some weight on, but I cannot remember which one it is... any suggestions? He isn't incredibly thin, just thinner than I like him to be. Which would be better to look into for a "new" food for him higher protein or higher fat or both? Right now he is at 21% protein and 10%fat... I would like him to gain 5-10lbs min but no more than 15ish. Any help would be appreciated!