i agree with others. his body condition is more critical. if he was really starving, he would be showing ribs. if i let my dogs eat whenever they acted hungry, they would outweigh me.
having said that, while the Diamond products tend to be cheaper, their value gets diminished by the fact that many of their foods have some of the lowest calorie counts per cup in their class. Diamond Naturals has only 368 calories/cup. Diamonds grain free food, TOTW, has only 370 calories/cup which is very low for a grain free, presumably more meat filled food.
it is not uncommon at all for people to be feeding quite a bit more of the lower calorie foods vs higher calorie, more meat based foods. i discovered a couple years ago that Orijen only costs me $4 more per month to feed than TOTW because i was able to feed so much less of it.
so, the cheaper foods dont always turn out to be the cheapest or as much of a value as they appear on paper.
as far as diamond produced grain free foods, i see Canidae grain free as a stronger value at around 120 calories more per cup than TOTW. my suspicion with TOTW is that it is less meat based than other grain free foods. i also dont like that they use ocean fish meal as the main meat source in their fish formula, as there is no way to know from month to month what comprises the ocean fish (and the fact that the fish they use is preserved with ethoxyquin).
grain free foods i like to use in my rotation:
Orijen
Acana Procincials
Wellness Core
i have liked results ive gotten from Canidae grain free, but made a personal decision about a year ago to stay away from Diamond products.