Lab studies measuring actual flatus output consistently find that men and women produce roughly the same volume of gas. The handful of controlled experiments that have bothered to measure this directly report no significant sex-based difference in either how much gas leaves the body or how frequently it does. So the premise of the question is a bit misleading, but the perception behind it is real, and the reasons it persists touch on everything from sphincter anatomy to social norms to the menstrual cycle.
What Controlled Studies Actually Measured
Gas studies are not exactly the most glamorous branch of gastroenterology, so there aren’t many of them. But the ones that exist are fairly consistent. A study in the journal Gut that placed rectal catheters in ten healthy volunteers (five men, five women) on a standardized diet found that the two groups expelled equivalent amounts of flatus over the measurement period.1PubMed Central. Investigation of normal flatus production in healthy volunteers A separate study that tracked flatus frequency specifically concluded that gender, age, and the ability of gut bacteria to produce methane had no significant influence on how often participants passed gas, whether on a baseline diet or one supplemented with a fermentable sugar.2PubMed. Factors influencing frequency of flatus emission by healthy subjects
These are small studies, and the field hasn’t exactly rushed to replicate them at scale. But their findings align: when you control for diet and measure the output directly, the sex difference disappears. Whatever is driving the widespread belief that men fart more, it isn’t a fundamental difference in gas production.
Sphincter Pressure and the “Holding It In” Factor
One of the more plausible explanations for the perception gap has to do with how and when gas is released, not how much is produced. The anal sphincter muscles that control gas passage differ between the sexes. Studies consistently find that men have higher resting and squeeze pressures in the anal canal. One study of anorectal function in healthy adults reported that men’s maximum resting pressure was about 91 cm water compared with 61 in women, and maximum squeeze pressure was roughly 257 versus 107.3PubMed. Anorectal function in normal human subjects: effect of gender A larger study using high-resolution manometry confirmed that men had higher resting pressure and significantly higher squeeze pressure than women.4PubMed. Gender differences in chronic constipation on anorectal motility The anal sphincter itself is physically longer in men as well.5PubMed. Anorectal manometric parameters are influenced by gender and age in subjects with normal bowel function
What does this mean in practice? A stronger sphincter with higher resting tone can hold gas against higher internal pressure before releasing it. When it does release, the gas may come out more forcefully and audibly. A lower-pressure sphincter may allow gas to seep out in smaller, quieter increments. So men might not be producing more gas, but they could be accumulating it and releasing it in more noticeable bursts. Meanwhile, women may pass the same total volume of gas throughout the day in ways that attract far less attention.
Add social conditioning on top of this anatomy and the perception gap makes more sense. In most cultures, women face stronger social pressure to suppress or conceal flatulence. That doesn’t eliminate gas. It just redirects how, where, and when it escapes.
Transit Time Differences Between the Sexes
Even though total gas output looks similar, the gut mechanics underlying gas production and movement differ between men and women in ways that matter. One of the most consistent findings in gastroenterology is that food moves through the colon faster in men than in women. A study tracking gastrointestinal transit in healthy adults found that colonic transit was significantly faster in men, along with more rapid gastric emptying after the initial lag phase.6PubMed Central. Variability of gastrointestinal transit in healthy women and men
A comprehensive review of the evidence on gut transit confirmed this pattern and added an important detail: the sex difference is most pronounced in the distal colon, with women having notably longer transit times through the transverse and descending portions. This holds even when researchers adjust for total calorie intake, diet composition, body weight, and height.7PubMed. Advancing human gut microbiota research by considering gut transit time Epidemiological data from the same review notes that women are more prone to developing constipation, which tracks with the slower motility.
You might assume slower transit would mean more fermentation time, more gas, and therefore more flatulence in women. And in some respects that’s true for bloating and discomfort. But slower transit also means gas has more time to be absorbed back into the bloodstream through the intestinal wall, or to be consumed by other microbes before it reaches the exit. Faster colonic transit in men could mean that gas produced by fermentation gets swept toward the rectum more efficiently, leading to more obvious and frequent expulsion even if the total volume is similar.
Colon length adds another wrinkle. A CT colonography study found that women’s colons are significantly longer on average than men’s, measuring about 154 cm compared with 147 cm.8PubMed Central. Bowel habits and gender correlate with colon length measured by CT colonography A longer colon combined with slower transit creates more surface area and more time for gas reabsorption or microbial gas consumption, which could partially offset any extra fermentation.
The Hormonal Dimension
The transit time difference between the sexes isn’t just structural. It’s heavily influenced by sex hormones, particularly estrogen and progesterone. Estrogen slows intestinal motility by triggering the release of nitric oxide, which relaxes smooth muscle in the gut wall. In animal studies, both estradiol and a synthetic estrogen receptor agonist prolonged colonic transit times in male and female mice alike and inhibited colonic muscle contraction directly.9Frontiers in Endocrinology. Sex-Bias in Irritable Bowel Syndrome: Linking Steroids to the Gut-Brain Axis Lab work on rat colon tissue has shown that estrogen superfusion inhibits spontaneous contractile activity in both sexes, and progesterone similarly damps down contractions in female tissue. Testosterone, by contrast, inhibits spontaneous contractions in male tissue but increases the response to stimulation afterward.10PubMed. In vitro spontaneous contractile activity of colonic smooth muscle in naive Lewis rats: Acute effect of gonadal hormones
The practical upshot is that in premenopausal women, circulating estrogen and progesterone keep the colon in a more relaxed, slower-moving state much of the time. In men, the hormonal environment may favor a colon that contracts more vigorously and pushes contents (including gas) along more quickly. This doesn’t mean men produce more gas. It means whatever gas they produce may arrive at the rectum sooner and more reliably.
Menstrual Cycle Fluctuations and Pregnancy
If you’ve ever noticed that your digestive patterns shift throughout the month, you’re not imagining it. The menstrual cycle creates a rolling experiment in gut motility. A study tracking microbiome activity and flatulence across cycle phases found that higher concentrations of flatulence peaks occurred during the ovulation phase, when transit speeds up briefly compared to the luteal phase that follows.11University of Maryland Digital Repository. The Relationship Between Gut Motility and the Phases of the Menstrual Cycle The reasoning: when transit time drops, fewer carbohydrates get fully absorbed in the small intestine, so more undigested material reaches the colon where bacteria ferment it and produce gas. In the late luteal phase, when progesterone peaks, transit slows back down and bloating becomes a more common complaint, with gas often retained rather than passed.
Pregnancy amplifies these hormonal effects dramatically. A review of gastrointestinal motility during pregnancy found that motility changes occur throughout the entire digestive tract, including a decrease in the rate of small-bowel and colonic transit that manifests primarily as bloating and constipation. Progesterone drives most of these changes, with estrogen acting as a primer.12PubMed. Gastrointestinal motility disorders during pregnancy Pregnant women often report feeling extremely gassy, not because they produce vastly more gas, but because the gas they produce moves sluggishly and pools in the colon, causing discomfort and distension. Some of it gets reabsorbed. Some eventually passes. The experience is miserable but largely invisible to anyone else.
The Smell Question
Volume and frequency are only part of what people notice about flatulence. Odor matters too, and this is one area where a sex difference has been documented, though not in the direction most people expect. The sulfur-containing gases that give flatus its smell are hydrogen sulfide, methanethiol, and dimethyl sulfide. Of these, hydrogen sulfide is the primary culprit, and its concentration correlates strongly with how bad the flatus smells.13PubMed Central. Identification of gases responsible for the odour of human flatus and evaluation of a device purported to reduce this odour
The production of these sulfur gases depends heavily on the composition of the gut microbiome and the amount of sulfur-containing foods in the diet (think eggs, cruciferous vegetables, and meat). Research on sex differences in the gut microbiome has found that men and women harbor different profiles of certain bacterial groups, including butyrate-producing species that also play roles in sulfur metabolism.14Journal of Neurogastroenterology and Motility. Roles of Sex Hormones and Gender in the Gut Microbiota Dietary patterns also diverge: men in many populations eat more protein on average, especially meat, which provides the sulfur-containing amino acids that gut bacteria convert into hydrogen sulfide. So while the total volume of gas may be comparable, the cocktail of gases and how offensive they smell can differ between individuals and, on average, between the sexes.
Early studies actually suggested that women’s flatus, on a per-volume basis, tended to have higher sulfur concentrations. But men typically produce flatus in larger discrete events (for the sphincter pressure reasons discussed above), so the total sulfur load per episode could be higher, and the perceptual impact is certainly more dramatic when a large volume of sulfurous gas arrives all at once rather than seeping out gradually.
Diet and Carbonation
Most intestinal gas comes from bacterial fermentation of undigested carbohydrates, particularly fiber, resistant starch, and certain sugars like fructose and lactose. A study on dietary fiber from wheat found that fecal pH was more acidic in men than in women, a marker that reflects different patterns of microbial fermentation.15Cambridge University Press. The effect of age, sex and level of intake of dietary fibre from wheat on large-bowel function in thirty healthy subjects The study also noted that methane producers, regardless of sex, had higher fecal pH, lower stool weight, and slower transit times than non-producers, reinforcing that individual microbial composition matters at least as much as sex.
Swallowed air is the other major gas source, and it behaves differently in men and women too. An imaging study that tracked what happens after people drink carbonated beverages found that women retained significantly more liquid in the stomach, and that bloating correlated most strongly with total gastric volume.16PubMed Central. Men and Women Differ in Gastric Fluid Retention and Neural Activation after Consumption of Carbonated Beverages Men cleared the carbonated fluid from the stomach faster, which could mean more gas reaching the intestines sooner. But it also means men may belch out a greater proportion of swallowed air before it ever reaches the colon, where it would become flatus. The net effect on downstream gas production is hard to predict from this data alone.
Lifestyle patterns layer on top of physiology. Men in many countries consume more beer and carbonated soft drinks on average. Eating quickly, talking while chewing, and chewing gum all increase air swallowing. None of these are biologically sex-linked, but they track loosely with behavioral tendencies that differ across genders. You can change all of them without changing your biology.
Physical Activity and Gas Movement
Exercise genuinely helps move gas through and out of the intestines. A study that infused gas directly into participants’ guts found that about 45% of the gas was retained during rest, compared with only about 24% during mild physical activity. Abdominal symptoms like bloating and discomfort also improved with exercise.17PubMed. Physical activity and intestinal gas clearance in patients with bloating Upright posture and movement stimulate peristalsis and help gas move through the colon rather than pooling in pockets along the way.
This matters for the sex-difference question because physical activity patterns differ by gender in most populations. Men are more likely to engage in vigorous physical activity, particularly activities involving abdominal muscle engagement, which can mechanically assist gas transit. Meanwhile, sedentary periods at work, which affect both sexes, tend to increase gas retention and bloating regardless of how much gas is being produced. Someone who walks after a meal will pass more gas sooner than someone who sits at a desk, and they’ll feel less bloated while doing it.
Stress, Functional Gut Disorders, and the Brain-Gut Axis
Functional gastrointestinal disorders like irritable bowel syndrome are far more common in women than in men, and they’re strongly correlated with stress. A review of the brain-gut axis found that these disorders are increased in both prevalence and reported severity in women, and that sex and stress interact to worsen symptoms. Hormonal differences in motility and visceral sensitivity play a significant role in this disparity.18PubMed Central. Role of estrogen and stress on the brain-gut axis
This creates a paradox that the “men fart more” narrative completely misses. Women are more likely to experience gas-related symptoms (bloating, distension, abdominal pain, the feeling of trapped gas) even though they may not be passing more flatus. The gas sits in the gut longer, causes more discomfort, and contributes to a cycle where stress worsens motility, which worsens gas retention, which worsens the perception that something is wrong. Men, with faster colonic transit and less visceral sensitivity on average, may experience the same volume of gas as a non-event because it moves through quickly and exits without much fuss.
This is where the original question starts to look backward. The question “why do men fart more?” frames male flatulence as the anomaly that needs explaining. But the research suggests it might be more accurate to ask why women’s gas is less visible despite being roughly equivalent in total volume. The answer is a layered interaction of hormones, anatomy, transit mechanics, and social behavior that conspires to make women’s flatulence less audible, less frequent in discrete episodes, and more likely to manifest as internal discomfort rather than an obvious external event. Men aren’t overproducing gas. Women’s gas is just better at hiding.
When Gas Actually Signals a Problem
For both sexes, passing gas anywhere from a handful to over twenty times a day falls within the normal range. The volume varies enormously based on diet, particularly how much fiber and fermentable carbohydrate you eat. A sudden and sustained change in flatulence frequency, especially when accompanied by other symptoms like weight loss, blood in the stool, persistent diarrhea, or severe cramping, warrants medical attention regardless of sex.
Certain conditions that cause excessive gas do have sex-skewed prevalence. Lactose intolerance, which drives fermentation of undigested lactose in the colon, affects men and women in roughly equal numbers but its expression varies by ethnicity far more than by sex. Celiac disease is diagnosed more often in women, possibly due to both genuine prevalence differences and diagnostic bias. Small intestinal bacterial overgrowth, where bacteria colonize the upper gut and ferment food prematurely, can cause extreme flatulence and bloating and appears to be more common in women, possibly linked to slower small-bowel transit. In all these cases, the gas isn’t just socially inconvenient; it’s a diagnostic clue.