i understand your concern that a weight loss by IT might increase his chances of being hurt as he hurtles his body through the air, careens off bigger players (ha, who isnt?), and bounces off the floor.
but, first, i dont think he has much "padding" at all now anyway. so i dont think he will become stick-like and more vulnerable. he is pretty fit and thin now.
second, i think by eat "healthy" it may create more energy and allow him to move more quickly for longer into the game. eating healthy does more than just cut one's weight (duh!) it increases strength and other benefits as well.
good for him and maybe even good for the rest of his life. i am not worried here.