Ffs, will the internet personal trainers do some proper research...... it's not muscle that he has put on he's FAT. His head is like a water melon, no definition in any part of his face, fat round face.
His stomach protudes.... visceral fat! Not just subcutaneous which is the stuff you can pinch - his stomach cavity is pushing outwards, he's lumping around at least an extra 15 pounds of fat for the extra 5 or 6 pound of muscle that he put on in his 7 or 8 weeks of "muscle building".
At Everton I would say he was 14.5st.... he's deffo nudging 16.5st at the moment.
he's an endomorph who like Rooney needs to do nothing more than high intensity cardio, kettle bell lifts, sledge runs, hill sprints. Difference is Rooney is a naturally strong coordinated aggressive bloke, lukaku isn't. Rooney when he did balloon could still cover 11km in a game cos he had heart and a desire for the team to do well.