The circadian rhythm, also known as the body's ‘internal clock,’ sets the stage for more than just sleep. It's not some imaginary concept coined by health gurus — the circadian rhythm encompasses multiple processes in the body regulated by a specific part of the brain called the suprachiasmatic nucleus, or SCN, located in the hypothalamus.
"Like a highly sophisticated computer processor, the SCN integrates light data received through our eyes and oscillates that information to every cell, organ, and tissue within the body to fine-tune the body's internal operations, from the secretion of hormones like melatonin and cortisol to the regulation of sleep-wake cycles and body temperature," says Serena Holtsinger, INHC, a Lifeforce Health Coach. "This makes light the master signal that both drives and entrains our circadian rhythms."
Fine-tuning these delicate processes lays the foundation for better sleep and energy — and can mean the difference between feeling your best versus functioning at 50 percent. In honor of World Sleep Day, here are the five best ways to optimize your circadian rhythm.
5 Ways to Optimize Your Circadian Rhythm
1. Expose Yourself to Morning Sunlight
Getting unfiltered morning light is incredibly beneficial for our energy levels, mood, focus, motivation, and metabolism. Dr. Andrew Huberman has drilled this habit into our minds and Holtsinger calls it "one of those non-negotiable health behaviors that pays dividends when done consistently over time."
“Morning light exposure has a dynamic balance of red, infrared, and blue wavelengths that can stimulate hormonal centers within the brain and help signal to the SCN to regulate our circadian clocks," Holtsinger says. "At the same time, our mitochondria are prompted to make pregnenolone, which turns into cortisol and sex hormones (such as estradiol, progesterone and testosterone), the former providing a hormonal ‘get up and go’ boost that gives us energy for the day."
Good sleep begins in the morning — and the light our skin and eyes are exposed to tells our body what processes it should be engaging in at any given time — even when we're sleeping. "We need sunlight during the day to maximize melatonin production in the evening, and the exposure to the balance of wavelengths in the morning helps our brain to understand what time melatonin should be released in the evening," Holtsinger says.
So it makes sense that this hormonal balance can be disrupted when you miss those morning light cues. If your goal is to boost your mental health, energy, focus, and motivation levels, get outside in the morning. Holtsinger recommends viewing the sunrise, opening a car window if you have a morning commute, or taking an early morning walk — but notes that both sunglasses and windows can decrease or block many of the wavelengths needed to receive the benefits.
2. Dim the Lights Before Bed
Well before you plan on hitting the hay, turn off the screens and dim the lights. "Gradually dimming ambient lighting as bedtime approaches emulates the natural dimming of light at dusk, preparing the body for sleep in a way that echoes our evolutionary adaptation to the setting sun," Holtsinger says. This gradual reduction in light intensity helps your body secrete the sleep-inducing hormone melatonin, according to a 2007 study in Progress In Neuro-Psychopharmacology & Biological Psychiatry.
Cortisol counteracts melatonin, and our constant, pervasive exposure to blue light from screens can mislead the SCN into perceiving it as daylight, prompting the release of cortisol and disrupting the natural sleep-wake cycle. "Even a mere eight lux of light — a level of brightness exceeded by most table lamps and about twice that of a night light — affects melatonin production," Holtsinger says.
The solution: Try blue light filters on electronics or turn them off altogether at least two hours before bedtime. Holtsinger also recommends using low-flicker red light bulbs in the bedroom and switching to "warm white" light bulbs instead of "cool white" bulbs when possible.
3. Get on a Consistent Sleep Schedule
If there’s one thing the body loves, it’s routine. "Sleep consistency is one of the primary keys to optimal daytime energy levels, mood, mental health, metabolic function, physical performance, and decreased risk of cancer and diabetes," Holtsinger says.
It turns out that stable sleep-wake times are a stronger predictor of mortality risk than how many hours you log. A 2024 study in Sleep looked at more than 60,000 people and found that folks with more irregular sleep patterns have a higher risk of premature mortality. Ideally, your sleep-wake times shouldn’t vary more than 30 minutes, every day — weekends included, Holtsinger says.
4. Eat Your Last Meal At Least 2 Hours Before Bed
Our circadian rhythms aren't only dictated by light exposure — meal timing also acts as an anchor for our body's internal clock. "Just as a train follows a timetable for optimal operation, eating meals at consistent times trains the body's metabolic processes to operate more efficiently, enhancing digestion, circadian alignment and sleep quality," Holtsinger says.
The circadian rhythm regulates our metabolism, and research shows that our eating patterns should take place during daylight hours when digestive efficiency and energy expenditure are at their peak, as suggested by a February 2023 review in the International Journal Of Molecular Sciences.
That's why Holtsinger recommends consuming your last meal or snack of the day at least two to three hours before sleep. That also means skipping out on that midnight snack. "Ideally, we want to keep our meal times as consistent as possible from day to day, with minimal caloric intake after dark," Holtsinger says.
5. Avoid Stressors Before Bedtime
As difficult as it may be to quit mindless scrolling before bed, minimizing stress before hitting the hay is an underrated yet key player in our circadian clocks. "Maintaining low stress levels before bedtime is crucial for optimal sleep due to the hormonal interplay of the stress hormone cortisol, which decreases at night, and melatonin, which signals sleep readiness and increases in the evening," Holtsinger says. "Elevated stress inhibits melatonin release and disrupts this balance, hindering sleep quality."
While we can't necessarily control every environmental factor we're exposed to, taking small, practical steps like deep, slow breathing through the nose and avoiding blue light from screens can make a big difference. Pinpointing your stressors is also key here. So if you know that watching the news or checking work emails triggers stress for you, make sure to avoid these altogether a few hours before bedtime. Also good to know: Avoiding caffeine past 2 p.m. (or earlier, for some) can help lower stress and align cortisol and melatonin levels for better sleep, Holtsinger says.
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This article was medically reviewed by Renae Thomas, MD, MPH; ABFM Board Certified in Family Medicine, ABPM Board Certified in Public Health, & General Preventive Medicine; ABLM Board Certified in Lifestyle Medicine.
