Mine eats all day! Breakfast , snack, morning tea, snack, lunch, snack lol.
Both boys eat a lot though. I have found weetbix and rice to be very helpful to fill them up! They eat a lot of fruit but thy doesn't really fill them up.

I am constantly fighting them off the fridge and cupboard! They even snapped the lock on the cupboard trying to get in!

My family in law ALL get grumpy if they don't eat! They get very irritable and cannot concentrate.
So I think it's quite common. He must be having a growth spurt Hun!