Why sleep timing matters

We’ve all heard it: Adults need 8 hours of sleep every night.

But sleep timing is just as important as sleep duration. Our bodies run on a circadian rhythm, a natural 24-hour clock that aligns with light and darkness. Historically, our bodies knew to wake with sunrise, and rest/sleep at sunset. This internal clock influences your hormones, thyroid, gut, metabolism, mood, energy, and more. But just because you’re getting enough sleep, doesn’t mean you’re getting it at the right time, and your body might be missing out on some key benefits of optimal sleep timing. Getting 8 hours of sleep from 1am-9am, for example, might not be as beneficial for your body the same way as getting sleep from 10pm-6am, for example. 

By sleeping later into the morning, you can miss the opportunity to get beneficial sunrise UVA light to help regulate your circadian rhythm for the day. UVA light is the first UV light to appear after sunrise, which is why early morning exposure helps signal to your brain that it’s daytime — kicking off your circadian rhythm and influencing hormone release like cortisol and serotonin. Just a few minutes of UVA light is beneficial, even if it’s a cloudy day. I’m grateful my dog requires me to take him outside each morning first thing as it forces me to get that early morning light in my eyeballs! Exposure to this morning light helps regulate:

• Metabolism

• Mood

• Hormone balance

• Gut health and digestion
  

Many of our hormones follow a rhythm that relies on sleeping during the early part of the night:

• Cortisol, your built-in energy and fat-burning hormone, is meant to rise with the sunrise—not several hours later.

• Melatonin, your body's nightly repair signal, kicks in earlier in the evening to support deep, restorative sleep, mitochondrial health, and immune repair.

• Leptin, which helps manage hunger and fullness, relies on a steady overnight rhythm to keep appetite and metabolism in check the next day.

• And growth hormone—essential for fat metabolism, muscle recovery, and healthy skin—peaks between 10 PM and 2 AM. If you’re still awake during that time, you’re likely missing out on one of your body’s most powerful repair windows.

When your sleep is out of sync with your natural circadian rhythm—from staying up too late and sleeping in—you can throw off key systems in the body. This can lead to more cravings, slower metabolism, trouble burning fat, low energy, mood swings, and sluggish digestion. You might also miss out on critical overnight repair, which affects everything from immune health to gut function. Even if you're getting 8 hours, if the timing is off, your body doesn’t function optimally.

What you can do:

Try to maintain a consistent sleep/wake cycle all days of the week (yes, even weekends!) so you don’t experience the “social jet lag” that can happen when your sleep is off by even an hour. Prioritize getting early morning sunlight by stepping outside for a few minutes each morning around sunrise (looking through the window doesn’t count!) to help reset your internal clock and encourage appropriate melatonin production in the evening. Work to fall asleep earlier in the evening if you’re a night owl with a goal to be in bed by 10pm. 

Your body was designed to heal and thrive in sync with the natural light-dark cycle. By honoring these rhythms, you’ll feel the difference in your energy, cravings, mood, and metabolism.