The connection between circadian rhythms & longevity

Your circadian rhythm is your body’s built-in 24-hour schedule.
It helps regulate when you feel awake and when you feel tired, but it also affects appetite, digestion, energy, and daily hormone fluctuations. In simple terms, your body likes routine—and it runs best when your internal clock matches the natural rhythm of daylight and darkness.

In this blog, we’ll look at what circadian rhythms are, how they change with age, why they matter for longevity, and what you can do to get your rhythm back on track.

In humans, the brain uses light signals detected by the eyes to keep time and sync the body’s internal clock. That’s why sleep, hunger, and focus often follow a predictable daily rhythm.

This rhythm is built in. Your body runs on “clock genes” that help keep a steady beat, but your everyday habits influence how stable that beat stays. Morning daylight, darker evenings, and consistent routines support healthy timing. Even small changes—like screen light at night, late dinners, or sleeping in—can disrupt your body’s timing.

Circadian rhythm and longevity

Once you understand what circadian rhythms are, the next question comes naturally: can timing influence how we age?

Researchers still focus on the basics like nourishing food, good sleep, movement, stress management, and daylight. In recent years, though, they’ve added a stronger emphasis on when these things happen and how consistent the daily pattern is.

The reason is simple: the body is not neutral across the day. It shifts gears in response to light and darkness, and key processes like hormone release, digestion, blood sugar control, body temperature, and recovery follow a daily rhythm. When sleep, meals, exercise, and light exposure vary a lot, the body can receive mixed signals.

A 2021 open-access review in Nature Communications, combining mechanistic research and human trials, highlights one clear example: dietary strategies can shape circadian organization, and meals can act as a daily time signal that helps metabolic tissues stay coordinated.

Classic longevity pathways meet the clock

The same review notes that circadian timing is closely linked to several well-known longevity pathways, including insulin and IGF-1 signaling, mTOR signaling, and sirtuins. What makes this especially interesting is that these pathways are not equally active all day long. Their activity can rise or fall depending on the time of day, and they are influenced by the body’s circadian system.

That is why researchers are testing a practical idea: if a pathway behaves differently across the day, then the same habit may not have the same impact at every hour.

Related: What are Sirtuins?

From theory to “circadian medicine”

The review also discusses circadian medicine, which is the idea that timing can influence outcomes because many biological processes shift across the day.

And you can feel the “when” in everyday life. Think about how different your body feels in the morning versus late evening. Earlier in the day, it often feels easier to get going and stay focused. Later, your system naturally starts preparing for rest. That lines up with daily hormone patterns: cortisol tends to be higher earlier, while melatonin rises later to support winding down.

This is why the same coffee can feel totally fine mid-morning but make you feel wired if it’s too late. It’s also why cravings often feel louder in the evening, and why you can feel strangely “awake” at 10 pm but heavy and foggy the next morning. The point isn’t that there’s one perfect schedule for everyone—it’s that your body doesn’t run on the same settings all day, so timing can matter more than people expect.

Related: How stress and cortisol impact aging

How circadian rhythms change as we age

If you sometimes think, “I used to handle late nights better,” you’re not imagining it. As we age, many people notice that sleep timing shifts and sleep becomes lighter. The 2021 Nature Communications review describes age-related changes in circadian function, including weaker rhythms and less stable synchronization to daily cues like light, meals, and routines.

In real life, this can look like getting sleepy earlier, waking earlier than you want, or having more broken sleep. It can also feel like your system is less forgiving: a late dinner, a bright evening, or a couple of “off” nights may affect you more than before. Jet lag is a great example—many people find it takes longer to recover as they get older, as if the body’s clock needs extra time to settle back into a new schedule.

Circadian rhythm and light

Light is the strongest cue your circadian rhythm uses to stay on time. A 2021 study makes that very real by following 51 people overwintering in Antarctica, where the normal day–night pattern disappears. The researchers looked at whether the body clock drifted out of sync with sleep, and what that meant in daily life. They found that when circadian timing and sleep timing were less aligned during the Antarctic winter, it was linked with poorer sleep and with differences in measures of mood and performance.

You don’t need polar night for this to matter, though. Bright indoor lighting and screens late in the evening can send your brain a “still daytime” signal, which can make it harder to wind down. On the other side, brighter mornings and dimmer evenings help your body keep a clearer day–night contrast, which many people notice as an easier time falling asleep and feeling more stable during the day.

Can blue-light blocking glasses help?

Blue-light blocking glasses reduce the amount of short-wavelength light reaching your eyes in the evening, which can help your brain get a clearer “night-time” signal and make it easier to wind down before bed. For some people they can be a useful support, especially if screens are hard to avoid. At the same time, when you look at the research as a whole, results are mixed. Some studies show improvements in sleep-related outcomes, while others find smaller or less consistent effects, so they’re best seen as a helpful tool rather than a guaranteed fix.

Health implications of circadian rhythms

Circadian rhythm disruption rarely shows up as just one symptom. It often feels like a pattern: sleep timing gets messy, energy becomes less predictable, cravings hit at familiar times, and your mood can feel more up and down. Research links circadian timing and misalignment to broader health outcomes, which helps explain why when can matter alongside what.

Sleep quality

When your circadian rhythm is stable, it helps your body build a natural sleep window, so falling asleep and waking up can feel more effortless. When the rhythm drifts, many people feel tired during the day but unusually alert in the evening. As the Antarctic findings earlier in this blog suggest, when internal timing and sleep timing don’t line up well, sleep quality and next-day functioning can take a hit.

Nutrition and weight control

Appetite and metabolism have a daily rhythm. That’s one reason cravings often feel stronger later in the day, even if you’ve eaten “normally.” In controlled human lab research, hunger and appetite naturally rise and fall across the day, and people tend to feel less hungry earlier and more hungry later. Another study supports the same overall pattern and suggests that appetite hormones like ghrelin may play a role when the body clock is out of sync.

Brain and mental health

Your brain is not in the same mode all day. Circadian timing shapes alertness and the ability to wind down, which is why a rhythm that drifts late can feel like a mind that won’t switch off at night. When circadian timing is out of sync, it can show up as irritability, lower motivation, brain fog, or feeling “wired” late and flat the next day—patterns that match what we see in real-world observations of misalignment affecting mood and performance.

Hormonal balance

Hormones follow daily patterns, and the circadian system helps keep that timing coordinated. A human-focused review explains how hormones such as melatonin, cortisol, leptin, and ghrelin are influenced by the interaction between sleep and the internal circadian system. So when your rhythm is pushed later by light or irregular routines, those signals can feel out of place, which often shows up as late-night alertness, evening cravings, or groggy mornings.

How to reset and fix your circadian rhythm

Resetting your circadian rhythm is mainly about sending your body clearer signals each day. The two biggest ones are light and routine. When mornings are brighter and evenings are calmer and dimmer, your body clock has an easier time keeping sleep and energy on track. Meal timing can support this too, since eating patterns can act as timing cues for metabolism.

Related blogs: GlyNAC and sleep improvement & What is NAD+: A vital molecule for health and longevity

Build your rhythm, support your longevity

A healthy circadian rhythm is one of the simplest ways to support sleep, energy, and daily balance. You do not need a perfect routine, just clear signals most days. When your mornings are brighter and your evenings are calmer and dimmer, many of the small “off” feelings tend to settle too.

If you want to support that routine from the inside as well, you can pair good timing habits with targeted supplements. Many people use Berberine as part of a metabolism-focused routine, GlyNAC as evening support for recovery and sleep, and NAD+ support for daytime energy. Think of supplements as a support layer that works best when your day-night rhythm is already heading in the right direction.

Support you circadian rhythm with supplements from Purovitalis, find them here.