I've been on Prilosec (Nexium, Prevacid, etc.) for years and no one who saw me would think I had any trouble digesting food :-) I'm not obese but definitely not skinny.
The problem for me, though (see post below) is that I've had a battle with yeast infections ever since I started taking that. I wonder if any other ladies out there have had this problem when taking proton pump inhibitors.