Are Women’s Intestines Longer Than Men’s?

Women do tend to have longer intestines than men, and the difference shows up in both the small intestine and the colon. A 2023 study published in PeerJ found that women had consistently and significantly longer small intestines, while multiple imaging and endoscopy studies over the past three decades have measured women’s colons as roughly 7 to 10 centimeters longer on average. The gap is real, but its size varies by study and measurement method, and the consequences reach further than you might expect.

How Large Is the Difference in the Colon

Several studies using different techniques have independently reached the same conclusion about the large intestine. A study using CT colonography found that women’s colons averaged about 154 centimeters compared with about 147 centimeters in men.¹ An earlier colonoscopy-based measurement put the gap wider, with women’s colons at a median of 155 centimeters and men’s at 145 centimeters, despite women being significantly shorter in stature.² A larger CT colonography study in over 500 adults reported women’s colons at about 193 centimeters versus 185 centimeters in men.³

The absolute numbers vary across studies because measurement techniques differ, but the direction is consistent: women’s colons are longer. And the specific segment that drives most of the difference is the transverse colon, the portion that stretches horizontally across the upper abdomen. One study found women’s transverse colons had a median length of 48 centimeters versus 40 centimeters in men.² The other major segments, including the rectum, sigmoid, descending colon, and ascending colon, showed no significant length difference between the sexes. The larger CT study confirmed that the transverse colon was the main contributor to the total length gap.³

The Small Intestine Story

The small intestine is far longer than the colon in everyone, typically stretching several meters, and it is also harder to measure precisely because it folds and loops extensively. A 2023 comparative anatomy study that examined human gastrointestinal tracts found that women had significantly longer small intestines than men.⁴ The researchers connected this finding to what they called the “female canalization hypothesis,” the idea that women’s bodies are better tuned for extracting nutrients, especially fats, from food. A longer small intestine means more surface area for absorption, which could provide a survival advantage during periods of nutritional stress like famine or pregnancy.

This finding is worth putting in context. The researchers themselves noted that gastrointestinal morphology data in humans have been surprisingly scarce. Limited data on gut variation have been collected since the late 1800s, and the topic was largely ignored for over a century.⁴ So while the sex difference in small intestinal length appears real, the evidence base is thinner than you might assume for such a basic anatomical question. Larger studies with more diverse populations would strengthen the picture considerably.

Why Measuring Guts Is Trickier Than It Sounds

One reason the data have been so sparse is that intestines are genuinely difficult to measure. The bowel changes length depending on whether you are measuring a living person during surgery, a freshly deceased cadaver, or a body preserved in formalin. A study comparing these methods found that formalin-fixed cadavers had significantly shorter small bowels than living subjects, averaging about 366 centimeters versus about 509 centimeters.⁵ Fresh cadavers landed in between, at roughly 593 centimeters. The intestinal wall contains smooth muscle that contracts and relaxes, so the length you get depends heavily on when and how you measure. This means that older anatomical studies, many of which relied on preserved cadavers, likely underestimated true intestinal lengths and may have obscured sex differences.

Modern CT colonography has improved the picture for the colon because it can estimate length in a living person without surgery. But the small intestine remains harder to image because of all that folding. The 2023 PeerJ study used a combination of cadaveric and fresh measurements, which strengthened the finding but still involved relatively small sample sizes. The field is genuinely playing catch-up on basic measurements most people assume were settled a long time ago.

How Pelvic Shape Factors In

One physical explanation for why women’s colons are longer, particularly the transverse colon, involves the shape of the pelvis. Women’s pelvises are wider and shallower than men’s, an adaptation for childbirth. This gives the abdominal organs a wider “floor” to rest on, but it also allows the transverse colon to drape lower. In the colonoscopy study that first identified the transverse colon as the main length difference, researchers found that the transverse colon reached the true pelvis in about 62 percent of women but only 26 percent of men.² In other words, the transverse colon in women does not just span the abdomen horizontally; it often dips down into the pelvis in a deep loop.

Research on how the gut relates to pelvic dimensions has found that in women, the volume of the gut does not scale with body size the way it does in men. This may reflect the competing demands on pelvic space: the pelvis needs to accommodate the reproductive organs and potentially a growing fetus, which limits how much the bony pelvis can support the abdominal viscera.⁶ The result is that women’s intestines are packed into a space that is shaped differently, not necessarily smaller, and the colon compensates in part by being longer and more mobile.

Slower Digestion in Women

A longer intestinal tract would, on its own, take longer for food to traverse. But the sex difference in digestive speed goes beyond what anatomy alone would predict, because hormones play a major role. Studies measuring how quickly food and waste move through the gut consistently find that women have slower transit. One study found that colonic transit was significantly faster in men, along with faster stomach emptying after a meal.⁷ Another study measuring transit through the stomach, small intestine, and colon found that all three segments showed significantly longer transit times in women.⁸

The hormonal component becomes especially clear when researchers look at the menstrual cycle. In one study, women in the luteal phase (the second half of the cycle, when progesterone levels peak) had nearly double the total colonic transit time compared with women in the follicular phase.⁹ Progesterone appears to slow the gut directly. Research shows that progesterone reduces the calcium signals that intestinal smooth muscle cells need to contract, essentially dampening the rhythmic squeezing that moves food along.¹⁰ A broader review confirmed that progesterone inhibits gut motility partly by increasing nitric oxide, which relaxes smooth muscle, and partly by blocking the signaling pathways that trigger contraction.¹¹

So women face a double effect: a structurally longer path for food to travel and a hormonal environment that slows the journey, especially during certain phases of the menstrual cycle. Estrogen also appears to influence gut function and the brain-gut axis, though its exact effects are less clearly established than progesterone’s.¹²

Why Colonoscopies Are Harder for Women

The longer, more mobile colon in women has a direct clinical consequence that gastroenterologists are well aware of: colonoscopy tends to be more difficult in women. The longer transverse colon, its tendency to loop into the pelvis, and the wider pelvic space that gives the colon more room to shift all make it harder for the endoscopist to advance the scope. One study found that women were the only independent factor associated with significant discomfort during colonoscopy.¹³ Another found that women were more likely to have incomplete exams and longer times to reach the end of the colon, and that thinner women were particularly challenging even when the endoscopist used thinner scopes.¹⁴

The thin-patient paradox is worth noting. You might expect a larger abdomen to create more difficulty, but the opposite is true. Less abdominal fat means less tissue to help hold the colon in a stable position, giving it more freedom to loop and bend. Body mass index was actually a predictor of exam length for both sexes: lower BMI meant longer procedures.¹⁴ This is one of those cases where a basic anatomical sex difference has a concrete, everyday medical impact. If you are a woman who has been told a colonoscopy will be straightforward, it is worth knowing that the procedure may take a bit longer and cause more discomfort than average, and that this has nothing to do with your pain tolerance and everything to do with your anatomy.

Constipation and the Longer Gut

Women are roughly twice as likely as men to experience constipation. A large study comparing symptoms between the sexes found that about 20 percent of women reported constipation compared with about 11 percent of men, with women having more than double the odds overall.¹⁵ A global meta-analysis using standardized diagnostic criteria confirmed the pattern across populations, finding that the odds of functional constipation in women were roughly two to two and a half times higher than in men, regardless of which set of criteria researchers used.¹⁶

Longer intestines and slower transit combine to make constipation a predictable consequence. The longer the colon, the more time the body has to absorb water from the stool, making it harder and drier. Progesterone’s slowing effect on gut motility adds to this, which is why many women notice that constipation worsens in the second half of their cycle or during pregnancy, when progesterone levels are highest. The anatomical and hormonal factors reinforce each other in a way that makes constipation not just more common in women but also harder to fully resolve with lifestyle changes alone.

Bloating, IBS, and Visceral Sensitivity

The sex differences in gut anatomy and motility also show up in irritable bowel syndrome, which is diagnosed about twice as often in women as in men. Female patients with IBS tend to report more constipation-predominant symptoms, more abdominal bloating, and more nausea than male patients. They also report greater sensitivity to food and more frequent side effects from medications.¹⁷

The bloating question is particularly interesting in the context of intestinal length. Women with IBS show heightened perception of colorectal sensations compared with men who have IBS, and the difference becomes even more pronounced after a meal or after a stressful stimulus in the gut.¹⁸ In healthy people without IBS, sex differences in visceral perception are not particularly strong. But once the gut becomes sensitized, the female tendency toward a longer and slower-transit colon that loops into the pelvis seems to amplify the problem. This helps explain why bloating is one of the most common and persistent complaints among women with digestive issues, and why it often fluctuates with the menstrual cycle.

Does Intestinal Length Affect How You Absorb Medications

Given that women have longer guts and slower transit, you might assume this changes how medications are absorbed. In theory, slower transit through the small intestine could increase the amount of drug absorbed (more time in contact with absorptive tissue), while slower colonic transit might affect drugs designed to release in the colon. But the research so far has not been able to pin this down with much confidence. A review examining gastrointestinal variability and drug absorption concluded that the link between colonic factors like transit time, sex differences, and drug absorption variability has not been firmly established.¹⁹

This is one of those areas where the anatomy and physiology strongly suggest there should be a meaningful difference, but clinical pharmacology has not caught up. Most drug dosing guidelines do not account for sex differences in intestinal length or transit time. Some researchers argue this contributes to the higher rate of medication side effects women report, though isolating gut anatomy as the cause from among all the other sex-based differences in drug metabolism (body composition, liver enzyme activity, kidney function) remains an open challenge. It is a gap that matters more than the field currently acknowledges, especially for drugs with narrow dosing windows where small changes in absorption timing could shift a patient from effective treatment into side effects.

Body Weight, BMI, and Colon Length

An underappreciated finding from the imaging studies is that body weight also affects colon length, and in the opposite direction from what many people would guess. One large CT colonography study found that adults with a BMI above 25 had significantly shorter colons than those with a BMI of 25 or below.³ The difference was about seven centimeters on average. The reason is not entirely clear, but it may relate to how increased abdominal fat compresses the colon into a tighter configuration, or it may reflect differences in the mesentery (the tissue that tethers the colon to the abdominal wall). Whatever the cause, it means the longest colons tend to belong to thin women, which loops back to the colonoscopy difficulty finding: thin women have the most mobile, loopy colons and the hardest time during the procedure.

The interaction between sex, body weight, and intestinal anatomy is a reminder that “women’s intestines are longer” is a population-level average, not a universal rule. A tall, heavy man could easily have a longer colon than a short, heavy woman. The sex-based difference becomes most pronounced when comparing men and women of similar stature and build, and it is most clinically relevant for thin women, who sit at the extreme end of colon length and mobility.

1
PubMed Central. Bowel habits and gender correlate with colon length measured by CT colonography
2
PubMed. Why is colonoscopy more difficult in women?
3
PubMed. Colorectal anatomy in adults at computed tomography colonography: normal distribution and the effect of age, sex, and body mass index
4
PubMed Central. Hidden diversity: comparative functional morphology of humans and other species
5
International Journal of Surgery Research and Practice. In Vivo Small Bowel Length is Longer than in Formalin-Fixed Cadavers
6
PubMed. Sexual dimorphism of the relationship between the gut and pelvis in humans
7
PubMed Central. Variability of gastrointestinal transit in healthy women and men
8
PubMed. Gastrointestinal mean transit times in young and middle-aged healthy subjects
9
The Korean Journal of Internal Medicine. Effects of Gender and Menstrual Cycle on Colonic Transit Time in Healthy Subjects
10
PubMed. Nongenomic effects of progesterone on human intestinal smooth muscle cells
11
PubMed Central. Progesterone inhibitory role on gastrointestinal motility
12
PubMed Central. Role of estrogen and stress on the brain-gut axis
13
Gastrointestinal Endoscopy. Factors affecting insertion time and patient discomfort during colonoscopy
14
Gastrointestinal Endoscopy. Colonoscopy in Women: Is It Still More Difficult Than Colonoscopy in Men and Is a Low BMI Still a Challenge?
15
PubMed Central. The influence of demographic characteristics on constipation symptoms: a detailed overview
16
The Lancet Gastroenterology & Hepatology. Global prevalence of functional constipation according to the Rome criteria: a systematic review and meta-analysis
17
PubMed. Gender-related differences in IBS symptoms
18
Gastroenterology. Gender-related differences in irritable bowel syndrome
19
Gastrointestinal Endoscopy. Impact of gastrointestinal tract variability on oral drug absorption and pharmacokinetics: An UNGAP review