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Why Flying to Compete May Cost Athletes More Than Just Sleep
In A Nutshell
- A new review suggests jet lag may disrupt both athletes’ body clocks and their gut bacteria at the same time.
- Eastward travel appears harder to recover from than westward travel, sometimes disrupting sleep for up to five days.
- Gut bacteria produce compounds that may help fuel muscles, and travel may reduce the amount available.
- The link between travel, gut health, and athletic performance is still largely unproven in real athletes, not a settled fact.
Elite athletes train for years to shave fractions of a second off their times. Their biggest obstacle might not be a rival or an injury. It could be the airplane ride to get there. A new narrative review in the journal Nutrients lays out a plausible chain of effects: long-distance travel may disrupt the body’s clock, and that disruption may scramble the gut’s microbial community.
For most people, jet lag means rough nights and daytime grogginess. For a professional athlete, even short-lived sleep and metabolic changes may matter more, since margins between winning and losing are so small. Researchers from Wroclaw Medical University in Poland reviewed studies suggesting rapid travel across time zones may alter gut bacteria, reduce molecules tied to muscle fuel, and trigger hormonal shifts lasting days.
Set to span six time zones across North America, the 2026 FIFA World Cup is, in the authors’ view, a fitting example of travel demands that could expose players to repeated disruption.
Eastward Flights Disrupt Athletes’ Sleep for Up to Five Days
A master biological clock in the brain coordinates sleep and wake cycles, hormone release, immune activity, and energy metabolism, with organs like the liver and gut following its cues through light and meal timing. When an athlete lands eight or nine time zones away, that clock does not instantly reset, clinging to the old schedule while the body tries to function on a new one, a mismatch called circadian misalignment.
One study of elite soccer players found eastward travel disrupted sleep for up to five days after arrival, specific to that group. Another, spanning 11 years of Super Rugby data, found meaningful performance drops among teams making roughly 24 hours of eastward travel across 12 time zones.
Direction seems to matter. Because the body’s internal cycle runs slightly longer than 24 hours, westward travel is easier to recover from than eastward. Recovery runs roughly 1.5 hours per day heading west, versus about 1 hour per day heading east, a gap that can become a real disadvantage for an athlete competing within days of an eastward flight.
‘Gut Jet Lag’ Drops Microbial Diversity in Most Travelers
Trillions of gut microorganisms follow their own daily rhythms tied to when a person eats and sleeps. When travel scrambles those patterns, the microbial community gets scrambled too, a mismatch researchers call “gut jet lag.” Evidence suggests it may be linked to a more permeable gut lining, meaning bacteria and their byproducts could leak into the bloodstream and trigger low-grade inflammation. That link is still a working theory rather than a proven cause in athletes.
One study of 267 non-athlete travelers found gut microbial diversity dropped in 61% of participants after their trip, particularly those who used antibiotics. A separate study of pilots found lower levels of beneficial bacteria than in fitness instructors, though the authors call this a small comparison, not a health finding about pilots.
Gut Bacteria May Fuel Muscle Through Short-Chain Fatty Acids
Beneficial gut bacteria produce short-chain fatty acids, small molecules made from dietary fiber that can serve as an energy source for muscle. Research cited in the review, much of it from animal studies, suggests these molecules may improve glucose uptake, support fat burning, and influence how muscles store glycogen, the primary fuel for high-intensity exercise. Scientists are still working out whether the same holds true in people.
Mice without gut microbes show reduced muscle mass and impaired fuel storage, and transplanting gut bacteria from endurance-trained athletes into mice raised glycogen stores in one study. When travel disrupts these microbes, athletes could plausibly lose metabolic support at a critical time, though nobody has confirmed that yet in real athletes.
Light Exposure and Probiotics May Ease Travel-Related Disruption
Travel brings added stressors beyond the time shift itself. Dehydration, intense exercise, and heat stress may reduce blood flow to the gut, straining the intestinal barrier, while athletes on the road are more likely to eat processed food, miss fresh produce, and eat at odd hours, all of which can push gut bacteria toward less beneficial states.
Researchers propose several strategies, though evidence for most remains limited in athletes: timed bright-light exposure to reset the body clock, melatonin after eastward flights, meal timing matched to the destination, probiotic and prebiotic supplementation, and adequate sleep, hydration, and fiber.
A Performance Gap Hidden in Plain Sight
An analysis of Olympic swimming found the fastest times occurred around 5:12 p.m., a 0.32% improvement over 8:00 a.m., a variation exceeding the gap between gold and silver in 40% of races, silver and bronze in 64%, and bronze and fourth in 61%.
That kind of gap raises a real possibility: circadian disruption could be quietly chipping away at athletes’ resilience in ways nobody has fully examined, though the authors call this a plausible concern requiring more research, not a settled conclusion. As competition calendars grow more demanding, travel, clocks, and gut health may prove to be one of sports science’s more important frontiers.
Disclaimer: This article is based on a narrative review, not a clinical trial, and describes proposed mechanisms and associations rather than established cause-and-effect findings. Readers should not treat any strategy mentioned here as medical advice or a substitute for guidance from a qualified physician, dietitian, or sports medicine professional.
Paper Notes
Limitations
This article is a narrative review, meaning the authors conducted a targeted, non-systematic search of existing literature rather than following a formal systematic review protocol. Studies were selected based on relevance to the conceptual framework, which introduces the possibility of selection bias. A substantial portion of the mechanistic evidence discussed comes from animal models, particularly rodent studies, whose findings may not translate directly to humans. Human studies cited are frequently based on small sample sizes, often limited to male endurance athletes, and of short duration, which restricts how broadly the conclusions can be applied. The review itself notes that direct evidence specifically in elite athletic populations remains limited across several key mechanisms discussed, including gut jet lag, microbiota-muscle interactions, and the proposed intervention strategies. Individual variation in diet, training load, and baseline gut microbial composition was not fully controlled in the studies reviewed.
Funding and Disclosures
According to the published paper, this study was supported by Wroclaw Medical University, which also covered the publication fees. The authors declare no conflicts of interest. The authors acknowledge that generative AI tools were used to assist with language refinement and stylistic editing, and that all content was reviewed and approved by the authors, who take full responsibility for the manuscript.
Publication Details
Paper Title: Travel-Induced Circadian and Microbiota Disturbances: Implications for Athlete Health and Performance: A Narrative Review | Authors: Karol Bilinski, Kacper Wisniewski, Laura Rafner, Pawel Witko, and Dagmara Gawel-Dabrowska (Wroclaw Medical University, Wroclaw, Poland) | Journal: Nutrients, Volume 18, Issue 10, Article 1523 (2026) | DOI: https://doi.org/10.3390/nu18101523 | Published: May 11, 2026
