Hatchling/juvenile dragons don't tend to get overweight - they're growing so fast and are so active they use it all in a short space of time. Yes they get large bellies but it's not a problem at that age... obesity issues occur closer to adulthood (around the 10 month mark onwards), when excessive feeding can lead to a big build up of fat stores (bulges behind the eyes, large tail base, chubby legs etc.)