Reminds me of Ready Player One, the book, not the movie

Never read it, nor seen it.

Without giving too much away, dystopian future, people escape their trouubles through a very powerful VR, and a contest to see who'll own the VR program.
Kodai's suit not fitting reminded me of the main character from at the least the book where in his downtime between finding the first and second MacGuffins of the story he ends up gaining so much weight he has trouble fitting in the largest of the suits needed to go into the VR and has no choice but to diet and exercise fearing that poor health would jeopardize his chances of winning the contest. Though it seems the movie doesn't use suits

Hah! That's actually kinda funny! Though Kodai doesn't have to worry about poor health despite his weight since his Zephyrite Genome bolsters his immune system and actively eliminates all threats to his physical body. In fact, it does such a good job at maintaining his health that many scientists who have studied him consider the Zephyrite Genome to be the long sought after "Fountain of Youth", or to use the terminology actually used in the story "The God Genome".