If I sleep too long (past 8 hrs) the same thing happens to me. It is super annoying bc I train a lot and don't have time to be feeling like that! For some reason 6.5 to 7 seems better for me. Have u tried to pllay with different amounts of sleep and how you feel?

Not to be give a snarky answer but if you as an individual do not need 10+ hours of sleep and 8 hours is sufficient for you that is what your body needs, do not try & force more sleep on it just because some people say to do it. I have had similar experiences where I have decided to just sleep in on a weekend and with that extra sleep I feel terrible, so I just get up at my regular time and have no issues :)

I can relate to this. I don't get a headache if I sleep too long, but I do feel groggy, have a low energy level and more aches for most the day, almost as if I'm getting over a cold. I know sleep is good, but I also feel that sitting still for too long can cause your blood to stagnate and lead to ill health effects. We all tend to recognize this when it comes to sitting at work, but I've never heard it mentioned when it comes to going to bed and sleeping. If you watch a movie or read and then sleep for 8-10 hours that could be somewhere in the 9 to 12 hour range of extended inactivity on a daily basis.

I've done some self testing on this and am noticing a correlation. So maybe there is something to be said for getting up and getting your blood flowing quicker having greater health effects than the exact recuperation of sleep. This would also synergize with all this new information about humans being biphastic sleepers in their natural state (two shorter stints of sleep, with a couple hours in the middle of high alertness as opposed to one extended sleep stint). Any thoughts on this idea?

If I sleep past 8 hours or so I also feel super groggy all day and just can't wake up properly. I think part of it is mental though...if I wake up at like 11:30 I just feel lazy and bad, like I've wasted half the day.

Yes! More than 8 hours and I am hungover for most of the day. It was like this for a while pre-primal too. 6-7 hours is ideal but less sleep is great as long as I don't build up too much of a sleep debt throughout the week - I got three hours last night and am still alert, I'll just feel sleepy in the evening, which doesn't usually happen (although I always fall asleep within 10 minutes of getting into bed).

I still have a tendency to sleep too much (it was a huge problem for most of my teenage years and early 20s when I was depressed and ate an awful 80%-wheat diet - I would got for 14 or 15 hours and still feel exhausted), which is to say more than 8 hours, and often have trouble waking/getting out of bed in the morning. I am not at all low-carb anymore, but waking more easily and feeling immediately alert was one thing that was much better when I was. I am thinking I need to stop eating carbs in the evening, so I can wake more naturally and not feel logey.

yeah same here.. I did that last night and it feels like dehydration to me.. your body loses water while you sleep (breathing + sweat) and also electrolytes and your blood sugar will also be low.. if you are asleep for a long time your body gets a build up of toxins.. due to you not being able to expel them and not drinking water (10.5 hours is a long time with no water).. get a big drink and see if it helps. they call it a sleep hangover, it is quite common.

This happens to me too. No problems though if I get up at my regular time, walk the dog, then go back to bed for a few more hours. That makes for a delicious Saturday morning.