Looking at a few different foods. It seems a lot of the senior formulas would be potentially suitable. But this is just me browsing right now.
Blue Buffalo Senior -
Blue Buffalo - Senior Dogs All Natural Dog Food
NB Reduced Calorie -
Dick Van Patten's Natural Balance Original Ultra Reduced Calorie Formula for Dogs
Artemis Weight Mgt. -
Artemis - Holistic Approach to Pet Food (this is lowest fat I've found - 6%)