Time-Restricted Eating: It’s Not Just What You Eat, but When

Parsley Health
Medically Reviewed
April 26, 2023

Time-restricted eating is having a moment in the health and wellness sphere. Also known as chrononutrition, time-restricted eating focuses on how when you eat impacts your overall health.

Evidence suggests that, when done correctly, eating on a schedule that works with your natural rhythms has lots of benefits, from helping you sleep better, to improving your cardiovascular health , to supporting a healthy gut microbiome , and much more.

The basics of chrononutrition

Even if chrononutrition is new to you, you’ve probably heard of intermittent fasting (IF), which is when you cycle between periods of eating and periods of fasting . (IF fans also use the term “intermittent feasting,” since IF also includes the part where you eat again!) Studies suggest that IF may improve cholesterol levels, glucose metabolization, insulin resistance , and even cognitive function . It may also reduce autoimmune disease and boost natural levels of anti-aging hormone DHEA.

But IF is an umbrella term for a lot of different approaches to time-restricted eating. One subtype of IF that’s growing in popularity is circadian rhythm fasting, which prioritizes eating based on your body’s internal clock—or circadian rhythms.

What is your circadian rhythm?

Your circadian rhythm (also referred to as your sleep/wake cycle) is a 24-hour internal "clock" that regulates how awake and how tired you feel over the course of your day. Your sleep schedule, body temperature, hormone levels, and digestion are all greatly affected by your circadian rhythms. If your circadian rhythm is balanced, you feel your best. When it’s disrupted, your health can be affected.

Your hypothalamus, located deep in your brain, is what drives your circadian rhythm. This powerful structure is the main link between your endocrine system (which governs your hormones ) and your nervous system (your body’s command center). When it’s exposed to light, it sends out signals to the rest of your body telling it that it's time to wake up. When that light goes away, it sends out the signal that it's time to wind down for sleep. This is why you don’t get sleepy when you’re on your phone or watching TV late at night; the blue light emitted from your electronic devices tricks your brain and suppresses your natural production of melatonin, a hormone that plays a key role in sleep.

How food impacts your circadian rhythm

But light isn’t the only environmental factor that impacts your circadian rhythm. According to adjunct professor of nutrition at New York University, Lisa Young, PhD, RDN, “It is thought that aligning your meals with your circadian rhythm may be associated with various health improvements, including reduced risk for chronic disease like diabetes and hypertension.” Not only that, but time-restricted eating can support better sleep, too.

Improved mental health is another possible benefit of circadian rhythm fasting. Parsley Health’s Dr. Jaclyn Tolentino says that, "Allowing your natural circadian rhythm to shape your nutritional habits is a very intuitive approach to both eating and resting; it encourages you to focus on when you’re actually hungry, when your body is asking for energy, and when it’s ready to rest—and act accordingly."

Parsley Health Coach Jessica Marcus MS, RD, writes that while it has been long established that our sleep-wake cycles are dictated by our exposure to light, namely the sunlight, “newer research suggests that every cell in our body also runs on this circadian rhythm.” Work by researchers like Dr. Satchin Panda, Marcus writes, have found that “by simply restricting the timing of eating…while holding calorie intake constant was associated with improved metabolism, mitochondrial function, and autophagy (the body’s way of cleaning out damaged cells).”

Does my circadian rhythm need support?

Sleep and circadian rhythm disruptions can be caused by sleep deprivation , as well as major biological shifts (like postpartum, puberty, and menopause), or life changes, like getting a new job, illness, travel, or moving.

10 early signs of circadian rhythm disruption include:

  1. Feeling sleepy, unfocused, or irritable during the day
  2. Feeling worried, anxious, irritable, depressed, or having mood swings
  3. Relying on your alarm or your partner to get out of bed
  4. Sleeping in later than usual
  5. Taking a long time to wake up and feel alert
  6. Only starting to feel awake in the evening or just before bedtime
  7. Feeling like you need a nap to function properly
  8. Having difficulty concentrating or experiencing impulsive behaviors
  9. Craving caffeine and sugar
  10. Getting sick frequently

Some benefits of circadian rhythm fasting according to the CDC

  • Lower blood pressure
  • Lower LDL or “bad” cholesterol
  • Reduced cardiovascular disease
  • Improved cognitive ability
  • Reduced risk for chronic diseases
  • Improved mood
  • Optimized digestion
  • Help decrease unwanted body fat

Tips to get you started with circadian rhythm fasting

  • Reduce the window of time that you eat. If you eat breakfast at 7:00 a.m. and eat dinner at 8 p.m., try to shorten that timeframe of 13 hours down to 11 or 10.
  • Avoid late-night eating. If you eat during a time period when you're not expending much energy, you'll increase your hunger and appetite.
  • Don’t skip meals. Ignoring the body’s circadian rhythm with periods of prolonged food restriction will only cause further disruption.
  • Food quality still matters. Eating junk food in your shorter window of time will still deprive your body of the vitamins and minerals it needs to feel its healthiest.

Looking for more support for circadian rhythm fasting?

If you’ve tried things like meditation, melatonin, and mindfulness without any improvement to your sleep, you aren’t out of options. At Parsley Health, our doctor-led medical teams work closely with expert health coaches to dive deeper and find the root cause of sleep disturbances—analyzing things such as hormones, the gut microbiome, and cortisol levels to address any underlying imbalances that may be throwing off your circadian rhythm.

Want to chat through it? Schedule a free 15-minute call to find out how Parsley can support your health goals.

Parsley Health

Parsley Health is the doctor that helps you live healthier, longer, by treating the root cause of symptoms and conditions. Our medical teams—staffed by leading clinicians and health coaches—spend more time with you, order the right tests, and prescribe food, sleep and movement alongside medications so you can get better—and feel better.

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