Back in the day, I played Rugby at an amateur level. ‘Trained’ twice a week and the occasional night time run. 6’2” and around 14st 10lb . I could eat what I wanted, as much as I wanted and drink Guinness without putting weight on. All because I had a very good metabolism. Muscle also weighs more than fat as it’s denser. Now, at 68, I weigh 15st, watch what I eat, walk a lot and have an Irish Whiskey at night.
The point is, all people are different. Luke Shaw will always be that body shape whatever he does, perhaps he could lose some fat. Steve Bruce is a fatty now but Keano isn’t, two different types of human.