Why do I feel bloated after meals?

Bloating after a meal usually comes from gas in the gut. NIDDK, part of the US National Institutes of Health, explains that gas normally gets there in two ways: when you swallow air while eating and drinking, and when bacteria in the large intestine break down carbohydrates that the stomach and small intestine did not fully digest. Eating fast, fizzy drinks and certain foods can add to the gas, and fatty meals can add to the bloating. NIDDK says having some gas symptoms is normal, especially during or after meals. It is also very common: in a survey of 51,425 adults in 26 countries, nearly 18% felt bloated at least once a week.

Why does my stomach feel bloated after I eat?

NIDDK describes bloating as a feeling of fullness or swelling in the belly. When the belly actually becomes larger than usual, doctors call it distension. Only about half of people with bloating also have distension, so you can feel bloated even when your belly does not look bigger.

Air you swallow while eating

Everyone swallows a little air with food and drink. NIDDK says that air which does not come back up as a burp can move on into the intestines. You swallow more air when you:

• eat or drink too fast
• drink fizzy drinks
• chew gum or suck hard sweets
• smoke
• wear loose-fitting dentures

Carbohydrates the small intestine does not fully digest

Some sugars, starches and fibre are not fully digested in the stomach and small intestine. NIDDK explains that they travel on to the large intestine, where bacteria break them down and make gas in the process. The more of these carbohydrates you eat in one meal, the more gas there can be.

Large or fatty meals

NIDDK notes that some people have more gas symptoms when they eat high-fat foods, which can increase bloating, or when they eat too much fibre. Among its general tips, the NHS suggests eating smaller, more frequent meals instead of large meals, and not eating large meals late at night.

How common is bloating after meals?

Very common. Several large surveys have asked adults how often they feel bloated.

What the surveys found

In the global study by Sarah Ballou and colleagues, people who might have a condition that explained their bowel symptoms were left out. Bloating was reported less often in older age groups, and women were about twice as likely as men to report it. In the US survey by Oh, Chey and Spiegel, about 29% of those who had never sought care said they were managing it themselves or were uncomfortable talking about it with a doctor.

What these numbers can and cannot tell you

Both surveys asked people to report their own symptoms, and neither included Thailand. They show that feeling bloated is a common, everyday experience. They cannot tell you why you in particular feel bloated after meals.

Which everyday foods and drinks are linked to more gas?

NIDDK lists foods and drinks with carbohydrates that may lead to extra gas. A 2015 review by Iacovou and colleagues at Monash University looked at these carbohydrates in East and Southeast Asian cooking and named onion, garlic, shallots, beans and pulses, and wheat-based foods as common sources.

Foods with these carbohydrates in Thai meals

Many of these are everyday foods. The list shows which parts of a meal are more likely to make gas, not foods that everyone needs to avoid.

Why milk drinks can leave some Thai adults bloated

Milk contains a sugar called lactose, which an enzyme called lactase breaks down in the small intestine. In a 2004 study at Siriraj Hospital, Densupsoontorn and colleagues gave 25 g of lactose in water to 45 Thai volunteers aged 21 to 31 who usually drank a box of milk a day. Their breath was tested for hydrogen, a gas made when gut bacteria break down sugar that was not absorbed.

The study was small and included only young adults, so the numbers show that this is common among Thai adults rather than how any one person will react. The authors noted that symptoms were not so severe that people limited how much milk they drank.

Everyone reacts differently

MedlinePlus, from the US National Library of Medicine, notes that foods that produce gas in one person may not cause gas in another, and lists eating more slowly so you swallow less air among its tips. NIDDK says a doctor may ask you to keep a diary of what you eat and drink and your gas symptoms, which can help a doctor or dietitian work out whether certain foods are involved.

Which eating habits are linked to bloating?

How you eat matters as much as what you eat. The habits below come from NIDDK and NHS general guidance on gas and bloating.

Habits and why they matter

General guidance from the NHS and NIDDK

As general guidance for everyone, the NHS suggests chewing with your mouth closed, drinking plenty of water, eating smaller and more frequent meals, and exercising regularly. NIDDK lists eating slowly and, when possible, sitting down to eat instead of eating on the run. These are everyday habits, not a plan for a particular condition.

For bloating that comes with diarrhoea or constipation during busy weeks, see Stress gives me diarrhoea then constipation. What can I do? For an upset stomach after days of eating out, see Eating out for days and my stomach feels off. What can I do?

When should I see a doctor about bloating after meals?

Most bloating after meals is part of everyday life. NIDDK says to talk with a doctor if gas symptoms bother you, change suddenly, or come with other symptoms such as tummy pain, constipation, diarrhoea or weight loss.

See a doctor if

The NHS says to see a GP if:

• you feel bloated regularly
• you have tried changing your diet but still feel bloated
• you have bloating and weight loss you cannot explain
• you have bloating and blood in your poo

Get urgent advice if

The NHS advises an urgent appointment if bloating comes with vomiting, diarrhoea or constipation, a stomach ache, a high temperature, a swelling or lump in your tummy, a burning feeling in your chest, or if you cannot pee, poo or pass wind.

Go to the emergency department if

Call emergency services (1669 in Thailand) or go to the emergency department if you have bloating with a swollen stomach and a severe stomach ache that came on very suddenly, vomit that has blood in it or looks like coffee grounds, or severe difficulty breathing.

What to bring to the appointment

• a food and drink diary for one to two weeks, with the times bloating happened
• how fast and how late you usually eat
• any weight change and any change in your bowel habits
• any medicines you take regularly