I know you said grain-free, but Fromm has some really good formulas with lower cals/fat. Their Gold line and their Four Star. I'd almost rather see a food with some brown rice and barley than full of peas and potatoes. All formulas are low in ash, meaning most of the protein is coming from meat and high quality meat. But, yeah, I just looovee Fromm and their very reasonably priced. I just bought a 15lb bag of Fromm Classic Senior for my dads overweight dog for $18.99.
Earthborn is also a great deal, and I've heard lots of good things. Their Meadow Feast formula is lower in fat and cals than most. I really like Now! too but it's really expensive from what I've seen.
Brit & Jackson