Short answerThe nine most common causes of bloating are eating too fast, a sudden jump in fibre, constipation, fermentable carbohydrates such as FODMAPs, lactose intolerance, IBS, stress and a disrupted daily rhythm, hormonal changes, and occasionally something that needs a doctor. Start a seven day food and symptom diary before removing anything, because the cause is usually a pattern rather than a single food.
Almost everyone bloats sometimes. Gas is a normal by product of digestion, and a stomach that looks flatter in the morning than at night is normal too. Bloating becomes worth investigating when it is daily, when it is uncomfortable, or when it arrived suddenly and has not left.
Here are the nine causes that come up most often in practice, roughly in the order worth checking.
1. Eating too fast
Eating quickly means swallowing air, and it means large pieces of food arriving in a gut that expected them chewed. Both produce gas. A meal eaten in eight minutes at a desk is one of the most common causes of afternoon bloating, and one of the easiest to fix. Give it twenty minutes at a table.
2. A sudden jump in fibre
Fibre is good for you and the transition is not. Going from a low fibre diet to beans, lentils and wholegrains in one weekend gives your bacteria far more to ferment than they are used to, and fermentation makes gas. Increase over three to four weeks and drink more water while you do.
3. Constipation
If stool is moving slowly, everything behind it backs up and ferments for longer. Bloating that comes with infrequent or hard stools is usually a transit problem rather than a food problem. Fluid, fibre, movement and a consistent morning routine do more here than cutting foods out.
4. FODMAPs and other fermentable carbohydrates
Some carbohydrates are poorly absorbed in the small intestine and get fermented further down. Onions, garlic, wheat, apples, pears, beans and lactose in milk are common examples. For people with IBS these can be a genuine trigger. For most other people they are not, which is why cutting them out on a hunch so often fails. If you go down this route, read the low FODMAP diet explained first, because it is a short diagnostic phase, not a way of eating.
Not sure which of these is yours? A four week personalised programme that finds the pattern and tests it properly is The Gut Code.
5. Lactose intolerance
Most adults worldwide produce less lactase with age, and undigested lactose ferments. The giveaway is bloating, wind and looseness within a couple of hours of milk, ice cream or a large latte, while hard cheese and yoghurt cause less trouble because they contain less lactose.
6. IBS
Irritable bowel syndrome involves a gut that is both more sensitive and less predictable in how it moves. The same volume of gas that another person would not notice can be genuinely painful. IBS is diagnosed by your doctor after other causes are excluded, and it is managed rather than cured, usually with a mix of food, routine and stress work.
7. Stress and a disrupted daily rhythm
The gut has its own nervous system and it is wired directly to your brain. Under sustained pressure, motility changes, sensitivity increases and digestion gets deprioritised. This is why a stressful fortnight and a bloated fortnight so often coincide, with no change in diet at all.
8. Hormonal changes
Bloating that tracks the menstrual cycle, or that arrives with perimenopause, is common. Shifting oestrogen and progesterone affect both fluid balance and gut motility. It does not mean nothing can be done, but it does mean the answer is rarely another elimination diet.
9. Something that needs a doctor
Coeliac disease, small intestinal bacterial overgrowth, thyroid problems and, less commonly, ovarian and bowel conditions can all present as bloating. Get medical advice promptly if bloating is persistent and new, especially alongside weight loss you did not intend, bleeding, difficulty swallowing, vomiting, a family history of bowel or ovarian cancer, or if you are over 50. If you suspect coeliac disease, ask for the test before you remove gluten, because removing it first makes the result unreliable.
What to do this week
- Keep a simple diary for seven days: food, rough times, symptoms two hours later, sleep and a stress score out of five.
- Slow your meals down and put three to four hours between them.
- Walk for ten minutes after your largest meal.
- Change one thing at a time, and give each change a week before you judge it.
If the diary shows nothing obvious, the cause is usually a pattern rather than a food, and that is a better problem to have. Our guide on how to improve your gut health in four weeks works through that pattern in order.
Want someone to read the pattern with you? Four private sessions and a personalised plan: see The Gut Code.
Written by Suzan Raad, nutritionist and author of Epigenix, Epigenetic Awakening, Epigenetic Diet and Back to Babylon, and co-founder of 360 Degree Clinic in Surbiton, London. More about Suzan.
This article is nutrition and lifestyle education. It does not diagnose or treat any condition and does not replace advice from your doctor. If your symptoms are new, severe or persistent, please speak to a medical professional.
