system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how can some people function normally while needing substantially less sleep than other people?

Like how can some people who get only 5 or 6 hours of sleep every night function at the same level as someone who gets 8-10 hours of sleep a night?
gpt
This is something that is still debated. First, some people insist they only need 5 or 6 hours of sleep a night and then survive off sugar and coffee to stay awake. Very few people can actually do this healthily, but some can. Scientists have linked a gene to most of the people who survive on extremely little sleep, but it's still unsure what exactly does. But ignoring extremes, its probably mostly a matter of efficiency. 

For example. Given the exact same lifestyle otherwise, some people need around 2000 calories a day while another needs 2500 for the same lifestyle. So that is a matter of how efficiently their body processes calories. The same can be true of sleep. Someone whose body falls into deeper sleep more quickly and who has fewer periods of wakefulness might need less sleep than someone whose body needs a while longer to achieve the same depth of sleep. It also could be their brain just more effectively using the sleep. Some may be caused by personal sleep habits and some genetics. It would be more strange if everyone needed identical amounts of sleep.