I agree with BCSnob - first you need to know who is eating how much.
That being said, as my Aussie got up there in years, his digestive system just didn't utilize food as well (after my Vet ruled out a whole bunch of other ideas), so in his last couple of years, I was pouring the food to him. Also gave him Sam-E to help his liver. Lots of easy-to-digest stuff - I made HIM a scrambled-egg breakfast every morning, but didn't for Ed and myself....LOL! He also received limited-ingredient dog food for lunch, and dinner with people-food scraps added. Any other dog would have weigh triple what he did - but he still lost weight a teeny bit at a time. When I had to put him down do to a hip injury, he was thin, but still a happy guy.