How much sleep is little sleep?

Anything less than 6 isn’t enough but maybe 5 or less is “not enough”

your body's natural sleep cycle is 90 minutes....and 3 sleep cycles per day are required to fully flush out the brains waste byproducts (ammonia, etc..)

so, that means, on a regular basis, you need 4.5 hours of actual sleep per night...plus a 15 minute nap in the middle of the day when the sun is at its highest (this is what our ancestors did...typically around 1-2pm).   Most people sleep a lot more than they need.

When you feel like crap in the morning. And you are so tired even coffee doesn’t really help and just make you feel even more stressed. Differs from people to people for me it’s less than 5 hours 30 minutes for more than 3 days.

Anything less than 7-8 is really not good for your long-term health. Even getting 5 hours for only a week can do some serious damage. IB hours are brutal, but even assuming you finish at 1am and need to be in the office by 10am the next day, try your hardest to be in your bed and asleep by 2am so you can get 7 hours and have time to get to work on time. This book covers the topic very well and I strongly suggest reading it. Bottom line is 7-8 hours most nights, no less than 6 on rare occasions.

If you’re not hitting about 8 hours, you are severely harming your hormonal production (particularly testosterone). Can be a big impact in weight gain, lethargy, brain fog and depression.