I honestly I'd find it funny if emu tried to diet a rider for eating a shonen protag amount only to feel bad when he finds out about the driver causing hypermetabolism
Emu would probably be able to tell if a Rider has hypermetabolism if he did a checkup on them (which ofc he would). It has some pretty obvious symptoms aside from the appetite. Fine tremors, a fast heart rate, no weight gain despite all the eating, etc. He'd figure out real quick that something else is up.
I should know because I actually have hypermetabolism, specifically due to hyperthyroidism. I didn't gain much weight easily, especially when I was younger- and I ate a bowl of rice 3 times a day, every day. I had the tremors, but I chalked it up to anxiety/nerves/caffeine until my parents convinced me to check up with the company GP. She took one look at me and said "you need to see an endocrinologist" and here I am, two years later and taking meds for a overworking thyroid