Lifestyle choices only get you so far if you have to figbt against your circadian rhythm to wake up before the sun. Your body wants to stay up late and wake up late, so you just end up sleeping less.
Nurses, doctors, firefighters, parents, and a number of other professions around the world are well versed in adjusting their sleep schedules as needed. I don’t think your circadian rhythm is as fixed as you think it is
Some do, and they can work those jobs because their biology allows it. A big chunk of it are just in constant state of sleep deprivation though and are miserable. That will catch up to them eventually.
