Circadian Rhythm + Metabolism
This is Part 2 of our series on circadian rhythm — your body’s internal clock that influences everything from hormones to digestion to energy.
Last time, we talked about skin health.
This week, we’re talking metabolism — and how light, timing, and even your morning coffee can work with or against your hormones.
Your Internal Clock and Metabolic Health
Every organ has its own circadian rhythm — yes, even your pancreas, liver, and gut.
They depend on light, food, and sleep cues to stay in sync.
When those cues get out of rhythm (think: late-night scrolling, skipping breakfast, eating at odd hours), it confuses your body’s timing. The result?
Blood sugar swings, insulin resistance, fatigue, cravings, and disrupted digestion.
Light is the first input your brain receives each day. Morning sunlight signals cortisol to rise naturally, tells your liver and pancreas its “daytime,” and gets your metabolism moving.
And no, your phone screen is not a substitute for morning light! If that's you, stop reaching for it before you're fully awake (power off your phone at night or better yet leave it in another room when you sleep) — the cool blue glow tricks your brain into thinking it’s midday and throws off your natural rhythm before you’ve even gotten out of bed.
When that light cue never happens or when bright light hits your eyes late at night, your body’s timing gets scrambled.
Why It May Be Time to Rethink Intermittent Fasting
Intermittent fasting can be a great tool for some people — but not when it disconnects you from your circadian rhythm.
If you’re skipping breakfast, running on coffee, and eating your biggest meal late at night, your body reads that as stress. Your cortisol rises, your blood sugar regulation falters, and your sleep suffers.
Women in perimenopause and menopause are especially sensitive to this.
Fasting too long or eating too late can elevate stress hormones, tank thyroid conversion, and increase cravings the next day.
The sweet spot for most women?
Eating within the first hour or two of waking — ideally after some morning sunlight and movement. That tells your body: you’re safe, nourished, and it’s okay to burn fuel.
Your body needs that early meal as a safety signal — proof that it’s not in famine mode, so it can shift out of stress and into balance.
And about that coffee… yes, it’s delicious, but it’s also an appetite suppressant that can work against you. Starting your day with caffeine and no food keeps your body in “fight or flight” and reinforces the old diet mentality of restriction instead of nourishment.
The workaround… have food before or with your morning coffee.
So if you've been intermittent fasting and not feeling like it's addressing your concerns like stubborn weight loss, cravings and sleep issues… consider cutting back to a 12 hour “fast” between dinner and breakfast and see how that feels.
The Light–Hormone Connection
Your circadian rhythm orchestrates the dance between cortisol, insulin, leptin, and melatonin.
Cortisol should rise in the morning (to wake you up) and taper at night. Artificial light and stress keep it high too long.
Insulin sensitivity is strongest earlier in the day. Eating big meals late at night makes blood sugar regulation harder.
Leptin, your satiety hormone, depends on consistent sleep and mealtimes. When your rhythm’s off, you stay hungry, even when you’ve eaten enough.
Melatonin (your sleep hormone) can’t rise properly if you’re exposed to blue light at night.
This is why when you eat and when you sleep matters just as much as what you eat.
Practical Daily Strategies
Here’s how to support your metabolism through your circadian rhythm:
Morning light before screens. Step outside within 30–60 minutes of waking — even 5 minutes helps. Stare in the distance. Let the daylight hit your eyes. Take a deep breath or two.
Eat breakfast. Include protein and healthy fats to stabilize cortisol and blood sugar. Your body needs that early meal as a safety signal that you’re nourished and safe — not running on fumes. If you can eat your breakfast outside, even better.
Time your coffee. Wait 60–90 minutes after waking so cortisol peaks naturally first. Coffee on an empty stomach is an appetite suppressant that keeps your body in stress mode — if you are thinking that appetite supressant is good you may need to ditch diet mentality.
Keep meals consistent. Aim for roughly the same eating window each day (not grazing all day or eating too close to bedtime).
Dim the lights around sunset. Avoid bright screens 1–2 hours before bed to allow melatonin to rise.
Small shifts here make a big difference in how your body regulates energy, hormones, and cravings.
Closing
Your metabolism, hormones, and digestion don’t just respond to what’s on your plate — they respond to your timing.
When you honor your body’s internal clock, everything runs more smoothly: energy, mood, cravings, and sleep.
If you're looking for the missing pieces of your health puzzle so you can feel like yourself again, hit reply to schedule a discovery call with me.