Digestive symptoms

Bloating

Also called: abdominal bloating, bloated stomach, distension

Bloating is the sensation of pressure or fullness in the abdomen, usually with a visible increase in belly size by the end of the day. It is mostly caused by gas from gut bacteria fermenting food, plus water retention and slow gut transit. Almost everyone experiences it, and most cases are pattern-driven, not disease-driven.

What is actually happening

Bloating is the combined effect of three things. First, gas produced when bacteria ferment carbohydrates that did not get absorbed earlier in the gut. Second, water held in tissue around the gut and elsewhere. Third, the speed at which the gut moves food along, which decides how long fermentation has to build up.

All three change through the day, with the menstrual cycle, with stress, and with what you ate the night before. That is why most bloating feels worse by evening.

The three patterns most people sit in

  • Gas bloating: distension that gets visibly bigger after meals, often with wind. Usually fermentable carbohydrates (FODMAPs) or large meals.
  • Water bloating: puffy, ring-tight, no real wind. Usually high salt intake the day before, the second half of the menstrual cycle, or poor sleep.
  • Slow-transit bloating: feels heavy and stuck, often with infrequent or hard stools. Usually low fibre, low movement, or dehydration.

What usually moves the dial

  1. Stop eating 3 hours before bed. The single biggest fix for morning and next-day bloat.
  2. Walk for 10 to 15 minutes after meals. Helps gastric emptying and reduces post-meal distension.
  3. Drink water with meals, not after. Helps moisten fibre and reduces hard stools later.
  4. Check sodium the night before any morning that matters. Restaurant food and takeaways are repeat offenders.
  5. Track your cycle. In the luteal phase (the second half of the cycle), progesterone slows gut transit and increases water retention, so bloating in that window is often hormonally driven rather than triggered by food.

When bloating needs more than this

Bloating that is daily, painful, comes with weight loss, blood in stool, or that wakes you at night deserves a GP visit. Coeliac disease, SIBO, ovarian conditions, and inflammatory bowel disease can all present as bloating in the early stages, and a simple set of blood tests rules most of them out quickly.

Common questions

Why am I bloated even when I eat healthily?
Healthy food is often the culprit. High-fibre foods like beans, broccoli, onions, garlic, apples, and oats are rich in fermentable carbohydrates that gut bacteria turn into gas. The fix is rarely less fibre, it is more variety and slightly smaller portions until your bacteria adjust.
Why is my stomach flat in the morning and bloated by night?
That is the normal pattern. Overnight, the gut clears and water shifts. Through the day, food, water and gas accumulate. By evening the average belly is 1 to 4 cm bigger than at waking. It is not weight gain, it is normal fill.
Can stress make me bloated?
Yes, reliably. Stress slows gut motility and increases visceral sensitivity, which means the same volume of gas feels more uncomfortable. This is one reason bloating tends to spike during exam weeks, hard work cycles, and periods of bad sleep.
Is bloating the same as gas?
Related but not identical. Gas is the volume produced. Bloating is what you feel and see. People with sensitive guts can feel bloated with normal amounts of gas. People with low sensitivity can have lots of gas and not feel bloated at all.

Sources