Your body has a master clock (the ‘head timekeeper’) which sits in the hypothalamus in your brain. It runs on a 24-hour light-dark cycle (called your circadian rhythm). External ‘signals’ such as light, temperature, food intake, and food timing help keep the master clock in sync.
The synchronisation between the master clock and the other ‘little clocks’ throughout the rest of your body is key to organising your biology and keeping bodily processes rhythmically ticking along as they should.
But in today’s modern world, it’s common for the master body clock to be forced out of sync. For instance, long-haul flights, shift work, and twice-yearly clock changes are common culprits of body clock desynchronisation.
The 24-hour cycle of the gut microbiome
Your gut microbiome follows the same 24-hour cycle, likely driven by the master clock in your brain.
Although your gut microbiome is not directly exposed to light, the master clock still guides its activity, shaping both composition and function of gut microbes throughout the day to maintain a well-regulated and steady state.
In fact, lab studies in animals have found that removing clock genes in the hypothalamus of the brain results in gut microbes losing their rhythm.
But it’s not a one-way street. Research also suggests that the gut microbiome may influence clock genes in the brain through metabolites, like short-chain fatty acids (SCFAs), but these influences are subtler than their effects on the other ‘little clocks’ present throughout the body, including the heart, liver and lungs.
Spring forward
Every year at the beginning of spring, the clocks go forward and you lose an hour of sleep.
While clock changes help align day-to-day routines with daylight, it may also come with health consequences.
Generally, the spring clock change is considered more disruptive than the autumn clock change where you gain an hour of sleep.
Most people can adjust to the clock change with a little help, although some people adjust quicker than others.
Here are five science-backed ways to keep your body clock on track when the clocks go forward.
1. Gradually adjust your sleep schedule
In the week before the clock change, go to bed 15-30 minutes earlier than usual. Do the same with your meals. This helps your brain and gut adjust slowly.
2. Get out in the morning sun first thing
Natural early morning light exposure, especially sunlight, is the strongest signal for regulating your body clock and is linked to better sleep quality and quantity.
3. Limit caffeine after lunchtime
You don’t have to skip caffeine – just be mindful of timing. Ideally, try to minimise caffeine after lunchtime. Go for decaffeinated options, herbal or fruit teas instead.
This is because caffeine has a quarter life of around 10-12 hours meaning that if you consume caffeine at lunchtime, a quarter of the caffeine is still in your brain close to midnight which can disrupt sleep.
4. Avoid alcohol in the evening
Many people believe that alcohol helps them sleep, but the truth is quite the opposite.
Alcohol has a sedative effect, but sedation isn’t the same as sleep. In fact, alcohol, even in small amounts, can impair sleep.
5. Review our 20 science-backed sleep tips
Including tips on napping, screen time, the bedroom environment, eating, and more. Get the tips.
Summary
The spring forward clock change can temporarily disrupt your body clock. Simple strategies – like gradually adjusting your sleep schedule and being mindful of caffeine intake - can help your body (and gut microbiome) stay on schedule.
Sources
Interactions between Gut Microbiota, Host Circadian Rhythms, and Metabolic Diseases. (2025). Link.
The effect of alcohol on subsequent sleep in healthy adults: A systematic review and meta-analysis (2025). Link.
The role of sunlight in sleep regulation: analysis of morning, evening and late exposure. (2025). Link.
