Scientists Had 6,400 People Track 360,000 Farts. One Time Of Day Stood Out

If you've been thinking that it's about time someone did some serious scientific research into farting behavior, you're in luck. A 2026 study published in JAMA Network Open involved 6,400 people measuring 360,000 of their own farts, and documenting when they occurred. The results showed that farting became more common during one specific part of the day: the evening.

The participants recorded their farting behavior on mobile phones, using the perfectly named Chart Your Fart app. As far as possible, they were asked to enter a gas-passing incident as soon as it happened, but retrospective entry was permitted for those farts that occurred at inopportune moments. The measurements took place over at least two weekdays and one weekend day, and no one took part who had recently made a big change to their diet, since an increase in fiber intake could cause digestive issues such as excess gas and constipation.

The average number of days recorded per participant was 10, though one person kept recording for 97 days in total. The results were measured in flatus per day (fls/d) and the results gave an interesting insight into the average person's farting habits. The average across the whole group was 5 fls/d, with men farting slightly more often than women. The youngest age group, ranging from ages 14–25 recorded the fewest flatus per day, while the 26–45 age group had the most. Although the quantities of farts recorded were of interest to the researchers, and tied in with other methods of measuring bodily gas, the results also showed interesting patterns in how the flatulence varied throughout the day.

Early evening is when many of us sit down on the sofa to unwind and relax — and it seems that letting one slip out as we do is a common habit. The results from the study saw a noticeable rise in documented farts after 6 p.m., dropping again after 10 p.m. It must be noted, however, that the experiment did not continue into sleep, so there is no data as to what happens to the frequency of farting throughout the night.

As part of the study, the researchers also compared the average food and fiber intake of the general population across the day, and the peak in flatus correlated with an increase in fiber consumed. While the results don't show categorically that an increase in fiber directly causes increased flatulence, there was a gradual increase at lunchtime, followed by a dip mid-afternoon when fiber intake dropped, before the larger peak after the evening meal.

Farting happens when the gases from the digestive tract pass through the anus. Some are smelly, some are odorless, but it is a perfectly normal biological process, despite the embarrassing label we have chosen to assign to it. Eating high-fiber foods, including broccoli, beans, and cabbage, can increase the quantity of gas produced, which explains the correlation between an overall rise in fiber intake and a rise in flatulence shortly afterward.

While this research gives interesting insights into the habits and timings of people's digestive gas, it doesn't tell us everything. Singular incidents of farting were recorded, rather than volume, so there could have been a wide variation in the actual quantity of gas that was produced each time. A 1991 study published in Gut, which measured the volume of flatus using a rectal catheter, found that volume of gas ranged from 476 to 1,491 milliliters across individuals. While the participants in this particular study had added baked beans to their diet, meaning the results were not typical, it showed that individual flatulence amounts can differ significantly.

The fact that participants were recording this data while going about their regular lives without the help of fart-detecting Smart Underwear, means that instances may have been missed, and researchers pointed out that in many cases gas can be held in for social acceptance. The increased occurrence at the end of day could therefore correlate with a higher chance of people being in their own home rather than in company, and possibly more inclined to let nature take its course. 

There was also no possibility to track a day where no flatus occurred at all, meaning the averages could be artificially high if any such days did exist. However, the data from this study, recorded in real time, gives a useful picture of what flatulence naturally looks like, and shows that for most of us, a little more farting in the evening is perfectly normal.