Do you feel well-rested? Are you ready to get up when you wake up or do you feel like you want to stay in bed? I always wake up before my alarm, but it happens for two different reasons: 1. I have gotten enough rest and am ready to get up or 2. because I subconsciously know I'm going to have to get up (early) to do something and I wake up before my body has gotten enough rest (but still before my alarm). I can usually tell the difference, especially later on in the day when I feel exhausted. Do you wake before your alarm or the time you would set it for even on days when you don't have to get up for anything? I think that would be the best way to tell whether your body has adjusted to getting enough sleep.

I always assume when I wake before my alarm I am well rested - and it's time to get up and not try to snooze!

Personally I find the cleaner my diet, the less sleep I need - perhaps coincidence but I reason that my body has a lot less work to do, so sleep becomes a lot more efficient?

It's not conclusive. Seth Roberts had trouble with sleep where he would always wake up too early. He concluded it was three things, but the one that stuck with me the most and I find to be most influential is that he said it's natural for your body to wake up if it's expecting to eat soon. So if you've been eating a decent sized breakfast early in the morning, that may have an effect. It hasn't been happening as much since my breakfasts are less substantial but it was happening with me. Just a possibility.

I'd think you can recognize whether you're getting enough sleep or not. If you wake up, but feel tired and can't go back to sleep that's probably not the best thing. But if you wake up and feel like you're ready to start the day, that's probably great.

I don't know about you, but I only yawn when I'm tired. But I could live on 6.5/7 hours of sleep and never yawn.

The whole 8 hour thing is a myth imo. Doubt our ancestors were getting that on a night to night basis

This may sound funny, but when my mother was a teenager (she told me this), she would unconsciously but instinctively wake up BEFORE her alarm sounded (and turn it off) just so she didn't have to hear the awful noise it made. She was still tired, however, and still needed the sleep. I mean, when you think about, where were there alarms every morning a million years ago? A strong sound like that probably signaled danger. Your body consciously knows what sound the alarm makes, it probably doesn't like it, so it wakes you up before so you turn it off.

Just my thoughts, Good Luck.

It might mean that.

It might also mean that you have something called "terminal insomnia," which is waking up too early and being unable to get back to sleep, and which is frequently one symptom of depression.

Do you feel well-rested? I tend to associate yawning with sleepiness more than carbohydrates, but that's just me. There is some good research that people who are chronically sleep-deprived are unable to detect their own (objectively measurable) impairment. David Dinges at Penn is the guy doing the best research.

Some possible reasons for waking up early could be an increase in cortisol, depleted glycogen stores, or being fully rested. I survived on 5 - 6 hours of sleep for a couple years. I got a lot accomplished during that time. I felt good and was eating healthy. I never woke up to an alarm. Then, about 6 months ago, I forced myself (thanks, Paleo people) to start sleeping at least 7 hours by going to bed earlier. Now, I am regularly getting 7 - 8 hours of sleep (except for last night when I finally started participating on PaleoHacks...much like the first time I played ShapeShift on my iPhone) I feel even better than before. I have increased mental clarity and "brightness" in the mornings. It's a noticeable difference, not just a "maybe". Try experimenting for a couple weeks with an extra hour or so of sleep and see if you notice fewer yawns or other improvements.

Reading T.S. Wiley's "Lights Out", remember sleep time is seasonal. Night time is longer in the winter, shorter in the summer. She recommends going to bed 1-3 hours after sunset. Where I am right now it is getting dark at about 8 and light at about 6, so going to bed 1 hour after sunset would be 9-6 or 9 hours, 3 hours after sunset would be 11-6 or 7 hours.

I would try sleeping more for at least 3 nights, see how you feel, and if you feel no different go back to 7 hours.