Some dogs can eat until they get sick, and then eat some more, lol. He's a growing boy, and would need more food as he gets bigger. Those charts on the back of foods are just recommendations after all. If he is active, he would definitely need a little more food as well. Since he's lost weight, I think you would need to feed him a little more and see what happens next week. Go by his weight and body shape, and determine whether to feed more or less from that. If he is gaining a stead amount of weight and isn't looking tubby, keep feed him that amount. Buuut, if he's getting fat and not looking so slim anymore, feed less, lol. I hope this helps. You can always talk to your vet as well to see if the amounts he eats are sufficient for his rate of growth.