Probably not, I suspect he's never been asked to bulk up, that or he's found it hard in the past. It was the one thing that was really obvious, he couldn't hold the ball at the start he was too light weight. Must be quite good for the lad probably feels much stronger and able to take the hits...
Trossard isn't fat or tubby, that's a relaxed diaphragm. But I do suspect the club has asked him to build his muscle base up as he was getting washed off the ball too easy. I noted this after lock down his shoulders, traps and arms were much larger, he'd clearly spent a lot of time in the gym...