Ever notice how your body naturally starts to feel sleepy at night or more alert in the morning—even without an alarm clock? That’s your circadian rhythm at work. It’s your body’s internal clock, running on a roughly 24-hour cycle, that influences nearly every biological function—from when you sleep and wake, to how your hormones, digestion, and even mood fluctuate throughout the day.
According to sleep medicine and women’s health specialist Dr. Andrea Matsumura, “Your circadian rhythm isn’t just about sleep—it’s the foundation of your body’s entire timing system. Keeping it in sync is critical for both physical and mental health.
Let’s break down what your circadian rhythm does, how it affects your health, and what you can do to keep it running smoothly.
What Is a Circadian Rhythm?
Your circadian rhythm is governed by a part of your brain called the suprachiasmatic nucleus (SCN), located in the hypothalamus. This “master clock” responds to environmental cues—especially light and darkness—to tell your body when to be awake, alert, sleepy, or restful.
The cycle works like this:
- Morning light signals your brain to stop producing melatonin (the sleep hormone) and boost cortisol, helping you feel awake.
- As night approaches and light fades, melatonin production ramps up, preparing your body for sleep.
“Think of it as your body’s natural timing system,” says Dr. Matsumura. “When your internal clock is aligned with your lifestyle and environment, everything runs more smoothly—from sleep quality to metabolism.”
Why It Matters for Your Health
A misaligned circadian rhythm—caused by things like shift work, jet lag, late-night screen time, or inconsistent sleep schedules—can wreak havoc on your health.
Dr. Matsumura points out the wide-ranging consequences:
- Poor sleep quality and insomnia
- Increased risk of depression and anxiety
- Weakened immune system
- Higher chances of developing heart disease, diabetes, and obesity
- Brain fog, low energy, and mood swings
“When your circadian rhythm is disrupted, your body’s systems aren’t functioning at their optimal times, which puts stress on your health long term,” she explains.
How to Support a Healthy Circadian Rhythm
- Get Morning Sunlight
Exposure to natural light within the first hour of waking is one of the most powerful ways to reset your internal clock. “Sunlight tells your brain it’s daytime, which helps regulate melatonin and cortisol levels,” says Dr. Matsumura. - Keep a Consistent Sleep Schedule
Try going to bed and waking up at the same time every day—even on weekends. Your body thrives on predictability. - Limit Light at Night
Blue light from phones, tablets, and TVs can trick your brain into thinking it’s still daytime. Dr. Matsumura recommends limiting screen time at least 1–2 hours before bed and dimming household lights in the evening. - Avoid Late-Night Eating
Your body digests and metabolizes food more efficiently during the day. Eating too close to bedtime can confuse your internal clock and impact sleep.
Tune Into Your Natural Rhythm
Your circadian rhythm is more than just your sleep-wake cycle—it’s a crucial part of how your entire body functions. “When you work with your body’s clock instead of against it,” Dr. Matsumura says, “you sleep better, feel better, and support your long-term health.”
By tuning into your rhythm, you’re not just getting better rest—you’re building a healthier life. Take the Sleep Goddess Archetype quiz for more tips from Dr. Andrea Matsumura.
