
I would say you want him on a high quality food with good levels of protein and fats, but less of it. Make up for the lack of bulk by substituting half hsi food with vegetables, which wil fill him up, but won;t be digested.
With my own breed that tends to put on weight easily thsi seems to be the only way to go if you want to maintain conditon.
What I and many people have found with the high fibre diet foods, is that the dogs loose conditon, muscle tone and coat especially.