I just need to consider if I am missing something 
He's 10 months. Full of energy when out on his walks, never stops moving and we 'work' them (we have a Springer too) in the sense that we do scent work, use balls, hide treats etc. We also live rurally so they spend a lot of time chasing rabbits through corn fields and forests. Walks are not a gentle stroll in the park 
You can see his ribs, and pretty much every bloomin' bone 
We still feed him three times a day, more than the recommended measurements and he's on Millie's Wolfheart kibble. After taking advice from them, I moved him onto the 'working gundog' range, which has a higher proportion of protein in it.
He gets raw bones and chicken wings too.
He's wormed and up to date with all vaccinations. He's happy and gentle and a pleasure to own.
JUST SKINNY!!
I did meet both his parents, it was difficult to judge mum obviously, given she's just given birth but Dad was slim. Having said that, the breeder was a full time gamekeeper, his dogs were bred to work.
Am I missing anything? I don't really want to reduce the exercise as they both live for their walks.