Going to Bed at 9 PM vs. Midnight: Does It Really Matter?
In today’s 24/7 world, many of us sacrifice sleep for late-night productivity or entertainment (especially if our days are filled with stress and not enough "ME time"). Trust me - I get it!
I often hear the argument - "as long as I get 7-8 hours, the timing of bedtime doesn’t matter," but the science of circadian biology proves otherwise. The time you go to bed—whether at 9 PM or midnight—has a profound impact on your metabolism, hormones, and overall health.
Here’s why going to bed earlier is more than just extra sleep—it’s about optimizing your body’s natural rhythms.
The Science of Sleep Timing
Your body runs on a circadian clock—a 24-hour(ish) cycle regulated by the rise and fall of sunlight. This clock controls hormone production, digestion, and energy metabolism. The closer your sleep aligns with your circadian rhythm, the better your body functions.
9 PM: More Aligned with Circadian Rhythms (especially in winter)
Melatonin Surge: Pineal Melatonin, your sleep hormone, begins to rise as darkness falls (as long as you mitigate your light environment), peaking between 9 PM and midnight. Going to bed at 9 PM allows you to ride this natural wave, falling into deeper, restorative sleep earlier.
Growth Hormone (GH): GH, essential for muscle repair, fat metabolism, and cellular rejuvenation, is released during the first phase of slow-wave sleep (SWS), which is strongest earlier in the night.
Cortisol Decline: Cortisol, your stress hormone, should naturally drop in the evening (and cortisol opposes melatonin). Sleeping earlier ensures it remains low, preventing stress-related disruptions.
Leptin Signaling: The hormone leptin - which signals your appetite, thyroid, sex hormones, immune system, heart - and more - is meant to dock to the brain at the same time melatonin is surging. Going to bed earlier ensures this crucial signaling happens appropriately & helps support all of these systems the next day.
12 AM: Out of Sync with Nature (especially in winter)
Melatonin Mismatch: Delaying sleep suppresses melatonin production, which can impair your ability to fall into deep sleep, leaving you feeling groggier even with a full 8 hours.
Reduced Growth Hormone: The critical SWS phase diminishes as the night progresses. By staying up, you lose valuable GH surges, affecting fat metabolism, muscle repair, and recovery.
Cortisol Disruption: Staying up late (especially if your light environment is not mitigated) can lead to a "second wind," where cortisol spikes to keep you alert—making it harder to fall asleep and increasing stress on your body.
Poor Leptin Signaling: If leptin is unable to dock to the brain due to cortisol or insulin being elevated - or melatonin being low - appetite, thyroid, mood, sex hormones & immune system can all become dysregulated (especially if this becomes a pattern).
Metabolic and Hormonal Differences
Here’s what happens when you choose an earlier bedtime versus staying up late:
Metabolism
Early Bedtime: Optimizes fat-burning (lipolysis) and glucose metabolism, and allows more repair programs to run.
Late Bedtime: Increases insulin resistance, leading to sugar cravings and fat storage, especially around the abdomen.
Hunger Hormones (Leptin and Ghrelin)
Early Bedtime: Balances leptin (satiety hormone) and ghrelin (hunger hormone), reducing cravings and overeating.
Late Bedtime: Suppresses leptin and increases ghrelin, causing cravings- appetite issues and potentially a higher caloric intake.
Energy and Mood
Early Bedtime: Ensures cortisol peaks naturally in the morning, giving you sustained energy throughout the day.
Late Bedtime: Cortisol remains elevated into the night, leading to morning grogginess and difficulty concentrating.
The Growth Hormone Advantage of 9 PM
Why Timing Matters: Growth hormone release is tied to the first phase of SWS, which dominates early in the night. If you sleep at 9 PM, your body maximizes GH secretion, aiding in:
Fat Metabolism: GH stimulates the breakdown of fat stores for energy.
Muscle Repair: GH facilitates protein synthesis, helping repair and rebuild muscles.
Cellular Rejuvenation: GH promotes tissue repair and regeneration.
The Downside of Midnight: By delaying sleep, you shorten the SWS phase and potentially miss the peak GH release, reducing these metabolic and restorative benefits.
The Bottom Line: Timing Matters
Going to bed at 9 PM versus midnight isn’t just about logging hours—it’s about aligning with your body’s natural rhythms to support a better metabolism, hormone balance, and overall health/longevity. When you prioritize an earlier bedtime, especially during the winter months, you:
Maximize melatonin and growth hormone benefits.
Stabilize cortisol and blood sugar.
Support your body’s natural fat-burning and muscle-repair mechanisms.
Tips for Transitioning to an Earlier Bedtime
Dim the Lights: Use Blue blockers if your family is not on board & keep it DIM! 10 lux and below is what is needed the 3 hours before bedtime to support melatonin production. (use the MyCircadianApp to measure Lux)
Eat Earlier: Finish your last meal 3-4 hours before bedtime to optimize digestion.
Wind Down: Create an evening routine with calming activities like a warm bath or shower, reading or meditation (and put your phone down by 8pm if you can!).
Embrace Early Mornings: Use quiet pre-dawn hours for journaling, stretching, or a gentle start to your day.
Consider Magnesium -Click here for the brand I use (and use code SKW for 10% off): Magnesium is essential for managing stress and maintaining a calm, balanced mood, and this formula contains the full spectrum of 7 proven forms of magnesium to target every system in your body.
What to do about early wake ups?
Waking up early in the winter - before sunrise, is a natural response to your body aligning with its circadian rhythm.
Longer nights mean your sleep drive kicks in earlier, often leading to a full night's rest by 4 or 5 a.m.
This is part of an ancestral pattern called segmented sleep, where a period of early morning wakefulness was common and used for quiet reflection or relaxation.
If you wake up early, don’t stress—resisting it can increase cortisol (the stress hormone) and make it harder to fall back asleep. Instead, embrace this peaceful time for journaling, meditation, or simply enjoying the stillness before the day begins. It’s your body’s way of syncing with the slower rhythm of winter.
In summary - shifting your sleep schedule to align with your circadian biology, you’re not just sleeping better—you’re living better. Let this winter be your season of restful nights and revitalized mornings!
If you made it this far - Thank you for taking the time to read. Please feel free to share this with a friend of family member who you feel could benefit!
In Health 🌞,
Sarah
READING THIS ON THE WEB or forwarded from a friend? Don't miss future articles & get access to exclusive discounts and freebies - click here to subscribe!
PS - This newsletter is not medical advice nor a substitute for 1:1 care with a trusted practitioner!
Be notified of new events as soon as they are open & get special discounts for being a subscriber.
Unlock 10% Off Any Product In My Store*
*excluding the Sarah Kleiner Wellness Membership and my Course Bundle
We hate SPAM. We will never sell your information, for any reason.
