Author: Dr. Nimra Naqvi (MPhill Clinical Nutrition)| Faisalabad, Pakistan Last reviewed: June 2026
Quick answer: Yes. The cabbage soup diet almost always increases how often you poop, and for many people it loosens stools or causes mild diarrhea within the first day or two. That is not a detox or a sign the diet is “working.” It is your gut reacting to a sudden flood of insoluble fiber, fermentable carbohydrates (fructans), and a lot of water from the broth. A smaller group ends up constipated instead, usually from not drinking enough.
You started the diet to lose a few pounds. Two days in, the bigger change is happening in the bathroom, and now you are wondering whether that is normal or a problem.
It is normal. It is also the most predictable thing about this diet. Below is exactly why it happens, why some people get the opposite reaction, and the warning signs that mean you should stop and get checked rather than push through.
What the cabbage soup diet actually does to your gut
The cabbage soup diet is a short, very low calorie plan, usually run for seven days, built around eating large amounts of cabbage soup with a few extra foods allowed on certain days. It has been around since at least the 1980s and is promoted as a way to drop up to about 10 pounds in a week. Most of that early loss is water and glycogen, not fat, and it tends to come back once you eat normally again.
For your digestion, the problem is not cabbage itself. Cabbage is a healthy vegetable. The problem is the dose and the speed. You go from a normal mixed diet to bowls of fiber-and-water-heavy soup, several times a day, almost overnight. Your gut has no time to adjust, and four things hit it at once.
1. A sudden overload of insoluble fiber
Cabbage is high in fiber, much of it insoluble. Insoluble fiber does not dissolve in water. It adds bulk to stool and speeds material through the digestive tract, which is why it usually helps with constipation. The NHS and British Nutrition Foundation suggest adults aim for around 30g of fiber a day. On this diet you can blow past that figure by lunch, and your gut feels it.
2. Fructans, which pull water in and feed bacteria
Cabbage also contains fructans, a fermentable carbohydrate in the FODMAP family. The human body absorbs only about 5 to 15 percent of fructans in the small intestine, so most travel intact into the colon. There, two things happen: fructans draw water into the bowel and gut bacteria ferment them. The water makes stools looser and faster. The fermentation produces the gas and bloating that so often come with this diet.
3. A large volume of water from the broth
It is easy to forget the soup is mostly liquid. Fiber works by absorbing water, and the broth supplies plenty of it. More fluid plus more fiber means softer, bulkier, easier-to-pass stools, and more of them.
4. Very little protein or fat to slow things down
Protein and fat slow digestion and help regulate stool consistency. The cabbage soup diet is light on both. With that brake released and the fiber pedal pressed, transit speeds up and stools tend to run loose.
Put together, the surprise is not that the diet changes your bowels. It would be strange if it did not.
So is it diarrhea, or constipation? It depends on you
Here is the part most articles skip. The same diet sends some people running to the toilet and leaves others blocked up, and the difference usually comes down to three things.
| What you get | Why it happens |
|---|---|
| More frequent, softer stools or mild diarrhea | The common reaction: too much insoluble fiber and fructans, too fast, plus extra fluid speeding transit |
| Gas, bloating, cramping | Fructans fermenting in the colon, especially if you rarely eat much cabbage or other cruciferous veg |
| Constipation instead | A big jump in fiber without enough water leaves stool dry and hard to move |
In practice, the people who struggle most are almost always the ones who jumped straight from a low-fiber, low-vegetable diet to bowls of cabbage. Their gut bacteria are not used to that fermentable load yet, so they get the gas and the loose stools at the same time. Someone who already eats a lot of vegetables tends to notice far less.
Your hydration, your gut microbiome, and your personal tolerance to fiber decide which version you get.
No, it is not a “detox”
This one matters, because it shapes how people treat the diet. Increased pooping on cabbage soup is not toxins leaving your body. It reflects fiber intake and gut fermentation, nothing more. There is no clean-out happening. Treating diarrhea as proof of progress is how people talk themselves into pushing past discomfort they should listen to.
More movement is not the same as better gut health. They can even point in opposite directions.
How soon it starts and how long it lasts
Most people notice the change within 24 to 48 hours, often sooner. For healthy adults the gut usually starts adapting after a few days, and gas and loose stools ease as bacteria adjust to the fermentable load. The catch is that this diet only runs about a week, so for many people it ends right around the time their body would have settled. The discomfort and the diet finish together.
If loose stools are severe from the start, or get worse instead of better, that is not your gut adapting. That is a signal to stop.
Who should be cautious, and who should skip it
For a healthy adult, a few days of extra bathroom trips is uncomfortable, not dangerous. But this diet is a poor fit, and sometimes a genuinely bad idea, for several groups:
- Anyone with IBS, SIBO, or a sensitive gut. Fructans are a classic trigger. In people with irritable bowel syndrome, fermentable carbs that distend the bowel can set off cramping, bloating, diarrhea, or constipation. A high-fructan crash diet is close to the opposite of what most gut specialists advise.
- People with inflammatory bowel disease (Crohn’s, ulcerative colitis) or a history of bowel obstruction, who should check with a clinician before any big fiber change.
- Pregnant women, children, and older adults, for whom both dehydration and nutrient shortfalls carry more risk.
- Anyone on medication for blood sugar, thyroid, or other conditions, since a sudden large fiber load can affect how some medicines are absorbed.
If you are in one of these groups and still curious, the honest answer is to talk to a professional first rather than experiment. Our gut health and IBS nutrition team can tell you in one consultation whether a high-fiber plan is safe for your situation.
Read Also: Low-Fibre Diet for Colonoscopy: A Practical Guide to Eating Right Before Your Test
If you are going to try it anyway, protect your gut
I am not going to pretend this is a diet I recommend. But if you have decided to do it, a few things genuinely reduce the misery, and they all trace back to one idea: your gut hates sudden change, so soften the shock.
- Drink more water than you think you need. Fiber only works well when it has water to absorb. Aim for plenty of fluid through the day, more if stools are loose, because loose stools cost you water. In a hot climate this matters even more.
- Cook the cabbage well. Lightly boiling or braising cabbage reduces its fermentability compared with eating it raw, so well-cooked soup tends to be gentler than coleslaw.
- Do not treat more fiber as automatically better. The standard advice is to raise fiber gradually, by roughly 3g a week, not all in one day. This diet does the exact opposite, which is precisely why the symptoms hit so hard.
- Add a little protein if you can. Even within a modified version, a small protein source helps slow transit and keeps stools from running completely loose.
These steps reduce side effects. They do not turn a crash diet into a healthy one.
Warning signs that mean stop and get help
Most of the time, the bathroom changes are just uncomfortable. Occasionally they are not. Stop the diet and seek medical advice if you notice any of these:
- Diarrhea that is severe or frequent. As a rough line, 10 or more bowel movements a day, or fluid loss you cannot keep up with by drinking, can cause dangerous dehydration.
- Signs of dehydration: dizziness, a dry mouth, dark urine, passing very little urine, or feeling weak.
- Blood in your stool, black stools, or severe abdominal pain.
- Symptoms that last well beyond the diet, or keep getting worse instead of better.
Dehydration from diarrhea is more dangerous in children, older adults, and anyone with a weakened immune system. If that describes you or someone you are caring for, do not wait it out.
A better way to stay regular
If your real goal is regular, comfortable digestion, cabbage soup is the slow road taken at full speed. The thing that actually keeps people regular is dull by comparison: a steady, varied diet with fiber from vegetables, fruit, whole grains, beans, and seeds, raised gradually, with enough water and some protein and healthy fat in the mix. That gives you the bulking and the fermentation benefits without the shock, and it is something you can keep doing after day seven.
For weight, the same logic holds. The scale moves fast on this diet because of water, then moves back. A plan you can sustain beats a week you have to recover from.
If you want that mapped to your body and your routine, an online nutrition consultation with our clinical team is a more reliable starting point than an all-you-can-eat cabbage week. You can also get a quick sense of balanced portions with our free food plate calculator.
Read Also: Is the Mediterranean Diet Good for PCOS?
FAQs
No. Loose stools and mild diarrhea are the most common reaction, but some people get constipated instead, usually because they raised their fiber sharply without drinking enough water. Gas and bloating are common either way.
Usually within 24 to 48 hours, often sooner. The combination of fiber, fructans, and the liquid in the broth speeds things up fast.
No. More bowel movements come from fiber and gut fermentation, not from toxins being flushed out. Frequent stools are a side effect of an extreme dietary shift, not evidence of cleansing or better health.
For a healthy adult, a short run is generally low risk beyond discomfort. The concern is longer or repeated use, which is poorly balanced and can disrupt your gut and nutrition over time. People with IBS, IBD, or other gut conditions should check with a clinician before trying it at all.
Cabbage contains fructans, a fermentable carbohydrate. Most of it reaches the colon undigested, where bacteria ferment it and release gas. Eating large amounts suddenly, especially if you do not usually eat much cabbage, makes the effect stronger.
A balanced diet with fiber from a range of plants, raised gradually and paired with enough water, is gentler and far more sustainable than a cabbage-only week. If constipation is an ongoing problem, a nutrition consultation can identify the cause rather than just push fiber at it.
Cabbage soup will move your bowels. That was never really in doubt. The better question is whether a week of urgent bathroom trips and water-weight that bounces back is the trade you actually want, when steady eating gets you a calmer gut and keeps it.
If your digestion has felt off for a while, that is worth a proper conversation, not another crash diet. Talk to our clinical nutrition team and start from your actual situation.
Medical disclaimer: This article is for general information and is not a substitute for personalised medical advice. The cabbage soup diet is a short-term, low-calorie plan and is not recommended for ongoing use. If you have a medical condition, are pregnant, are caring for a child or older adult, or develop severe symptoms, consult a qualified healthcare professional before making dietary changes.
Read Also: What Causes Children to Walk on Their Toes?
DT Nimra Naqvi is an MPhil-qualified clinical nutritionist specialising in therapeutic, condition-specific nutrition care. She designs personalised nutrition plans for metabolic, hormonal, digestive, and recovery-related conditions, grounded in evidence-based practice. Her work focuses on integrating nutrition with medical treatment and rehabilitation to support sustainable health outcomes. DT Nimra Naqvi provides professional online consultations for international clients across the USA, UK, and Europe.
