Guide to Daylight Saving Time: Hormones, Sleep and Mood

The days are getting longer, the mornings brighter and the sun lingers past 5 pm – the clocks have just changed. Losing an hour in bed might not sound like a big deal, but for many of us, it hits the body harder than expected. That grogginess the next morning is just the tip of the iceberg. Your circadian rhythm – the internal clock that orchestrates sleep, wakefulness, metabolism and hormone release is tightly linked to the natural light-dark cycle. Even a seemingly small disruption, like losing one hour, can ripple through your system, affecting hormones that regulate energy, appetite, mood and more. For women, whose hormonal systems are particularly sensitive and cyclical, this shift can feel even more pronounced.

What’s important to know is that these effects aren’t always limited to just one day. If your body doesn’t adjust immediately, the disruption can accumulate over several days, amplifying fatigue, mood changes, cravings or menstrual-cycle-related symptoms. That’s why it’s common to feel “off” for a few days after the clocks spring forward, even if you get what seems like enough sleep. Supporting your circadian rhythm with consistent light exposure, sleep routines and balanced meals can help your body catch up more quickly.

 

The science behind your internal clock

Your circadian rhythm is a roughly 24-hour cycle that tells your body when to sleep, eat, be alert and even digest food efficiently. The master clock, located in the suprachiasmatic nucleus (SCN) of your brain, coordinates thousands of cellular clocks throughout your body. Light exposure is the most important signal, helping your body align its rhythms with the day-night cycle.

When your circadian rhythm is aligned, your hormones release at the right times: cortisol in the morning to help you wake, melatonin in the evening to prepare you for sleep and reproductive hormones like oestrogen and progesterone fluctuating in sync with your cycle. When the clocks spring forward, this rhythm is suddenly shifted and the effects can accumulate over a few days if your body struggles to adjust.

 

Hormones that feel the clock shift

• Cortisol: Often called the body’s “stress hormone,” cortisol isn’t just about stress – it’s essential for daily functioning. It helps regulate metabolism, blood sugar, immune response and wakefulness. Normally, cortisol peaks in the early morning to help you feel alert and energised. When the clocks spring forward, this peak can get delayed, leaving you groggy or mentally foggy. If your rhythm doesn’t reset quickly, this sluggish feeling can linger for several days.
  
  
• Melatonin: The “sleep hormone,” melatonin signals to your body that it’s time to wind down. Losing an hour can delay its release, making it harder to fall asleep at your usual bedtime. Over consecutive nights, reduced melatonin can amplify sleep debt, leaving you more tired and less focused.
  
  
• Oestrogen & Progesterone: These hormones naturally fluctuate throughout the menstrual cycle, influencing sleep, mood and energy. Circadian disruptions from losing sleep or misaligned light exposure can temporarily affect how your body regulates them. If your system doesn’t adjust quickly, you may notice lingering fatigue, mood changes or subtle menstrual-cycle-related effects.
  
  
• Insulin: Controls blood sugar and energy availability. Short-term circadian misalignment can reduce insulin sensitivity, leading to higher blood sugar spikes and increased cravings. Over several days, this can make energy dips or carb cravings more noticeable.
  
  
• Leptin & Ghrelin: Appetite hormones that signal fullness (leptin) and hunger (ghrelin). Disrupted sleep or delayed circadian cues can throw these signals off, making overeating or snacking more likely. If your body doesn’t adjust right away, these effects can compound over multiple days.

 

Practical Ways to Support Your Body During the Clock Change

Supporting your circadian rhythm doesn’t have to be complicated. Small, consistent habits can make a huge difference, especially in the days following the time change:

 

• Gradually adjust your bedtime: Go to bed 15–20 minutes earlier in the nights before and after the change to help melatonin shift naturally.

• Morning sunlight exposure: Sunlight shortly after waking helps reset your internal clock and supports cortisol alignment.

• Dim lights in the evening: Reduce blue light from screens and bright lamps to allow melatonin to rise.

• Keep meal times consistent: Balanced meals at regular times support insulin and leptin rhythms, helping maintain steady energy and appetite.

• Gentle movement: Morning exercise boosts alertness and aligns cortisol, while evening stretching or yoga promotes restful sleep.

 

• Honour your cycle: Track energy and mood through your menstrual cycle, and adjust routines for sleep, meals and activity accordingly.

 

Reset your clock

Springing forward might feel like just an hour lost, but your body experiences it as a mini jet lag. For women, whose hormones are already finely tuned, even small disruptions can affect sleep, mood, appetite and the menstrual cycle. These effects can accumulate over several days if your circadian rhythm doesn’t reset quickly, making it important to proactively support your internal clock.

By paying attention to light exposure, sleep habits, meal timing and gentle movement, you can ease the transition, keep your hormones balanced and stay energised throughout the day. Springing forward doesn’t have to throw your body off balance – support your internal clock and you’ll feel aligned, focused and ready to embrace longer days with the same energy and vitality.