If you’ve ever flown across multiple time zones on your way to a holiday, you’ve likely encountered jet lag - that groggy, disoriented feeling that hits when your body clock is out of sync with local time.
Jet lag is a temporary sleep disorder that happens when your circadian rhythm (your internal clock that regulates sleep and wake cycles over a 24-hour period) gets disrupted by rapid travel across time zones. In short, your body thinks it’s one time, but the local clock says otherwise. Let’s say you fly from London to Bangkok and arrive at your hotel at 10pm. You’re ready to sleep, but your body is still on UK time - which is 4pm - and no amount of herbal tea or relaxing playlists will help you nod off.
Since jet lag throws off your sleep-wake cycles, it’s no surprise that symptoms include daytime sleepiness, headaches, trouble concentrating, and low mood. But less recognised about are the gut problems - upset stomach, bloating, constipation. So what’s going on in your gut?
Gut lag is real
Just like your sleep is ruled by a 24-hour rhythm, so is your gut. Gut function follows a daily pattern, with slower activity at night (which is why you don’t need to poo at 2am) and more action during the day when you're eating and moving around.
When you travel across time zones and disrupt your sleep, your gut clock gets thrown off as well. The result? Symptoms like nausea, bloating, constipation, or feeling hungry at all the wrong times.
Flying itself can make these symptoms worse due to airport snacks, alcohol, cabin pressure (a known bloating trigger), and the stress of travel, think lost luggage, delayed flights, sitting still for hours. It all adds up. There’s also evidence that your gut microbes can be affected by time zone shifts, meal timing, and sleep patterns.
So is it gut lag or something I ate?
Jet lag and therefore gut lag tends to kick in when you cross three or more time zones. So flying from the UK to Australia, which spans 10 for example. Jet lag is generally worse when flying east, since you’re ‘shortening’ your day rather than lengthening it (as you would flying west).
If you’ve only crossed one or two time zones, your gut symptoms may be more about the travel itself than full-blown gut lag. In my experience, people with sensitive digestion, or who rely on routine for gut health, are more affected. Research has also linked disrupted circadian rhythms with gut problems like IBS and constipation, both of which can be aggravated by travel.
Your chronotype - whether you’re a morning lark or night owl - plays a role too. Morning types may find flying east a bit easier than night owls, while westward travel might be less disruptive overall.
How to minimise gut lag
The best way to manage gut lag is to help your body clock adjust to the new time zone. Here’s how to speed things up:
- Book smart: If you're prone to jet lag, consider booking a flight that lands during the day. Natural light helps kickstart your body clock. Once you land, take a walk, as exercise reinforces the reset.
- Start the shift early: A few days before your trip, begin moving your mealtimes and bedtime closer to the time zone you’re heading to, even by 30 minutes to an hour.
- Change your watch: Set it to your destination’s time as soon as you board the plane to start mentally adjusting.
- Get out in the light: Spend time outdoors in the morning at your destination. Even if it’s overcast, there is still way more light than indoors, and this helps reset your clock.
- Stay hydrated: Dehydration can worsen jet lag symptoms. Skip alcohol when you fly and drink plenty of water instead.
- Eat on local time: Get on track with meals at your destination’s timezone. Keep your evening meal light, but opt for a big brekkie. Recent research suggests that a big morning meal may help reset your body clock more effectively.
Join us as we uncover how you can feel your best inside and out this summer.
Sources
How to travel the world without jet lag. Sleep Medicine Clinics. (2009). Link.
Disruption of Circadian Rhythms and Gut Motility
An Overview of Underlying Mechanisms and Associated Pathologies. Journal of Clinical Gastroenterology. (2020). Link.
Insights about travel-related sleep disruption from 1.5 million nights of data. Oxford Academic. (2025). Link.
