We evolved to work within a daily cycle. Wake up with the sun, go to sleep at night. In your eye there are different types of light sensing cells. But some of these cells do NOT help you see. Some cells evolved BEFORE sight. These are there to regulate your body clock, your circadian rhythm.

But now we are all out of wack.

Basically we evolved to work within the daily cycle. Wake up with the sun, go to sleep with the night. Generally now we are all out of wack.

First, we are not signalling to our eyes light sensing cells that we are about to go to sleep. People mess with this by keeping lights on, staring at a phone before bed, etc. If you set up your habits so that you dim lights at night and limit phone usage , you will get better sleep, and feel more energized.

Second, we are not signalling to our eyes light sensing cells that it is time to wake up. The sun is the major trigger that you are missing. Indoor lights simply do not get to the same brightness. But, if you set your habits so that you go outside as soon as you wake up and see the sun , you will wake up better, get better sleep, and generally be more in sync.

If you do this, your body starts to get in sync with the day. You will find yourself hungry at the right times, tired when its time to go to bed, awake when it is time to do stuff.

These two videos explain it in detail very well.