A bloated belly: the causes, what a gut scan measures and when to see your GP

In this article you will read where a bloated belly comes from, what a gut scan measures and when to go to your GP. That matters, because when you know where the complaint can come from, you know better what you can do yourself. In the morning your trousers fit and by the end of the afternoon they do not. You undo the top button and you wonder what you ate that was wrong. A bloated belly rarely has one cause, and “too much gas” is almost never the explanation. The causes vary: what you eat, how your gut senses stimuli, how quickly the contents pass through and how your abdominal wall and diaphragm react. The BioProfile gut scan measures how much these complaints affect you, and gives you an indication of where you stand today in this area, as the first of the 11 health areas the full scan assesses. This is not a diagnosis. It is insight, to see where you stand today. And to help you make better choices in your food and lifestyle. What this scan does not do: point to a cause or make a diagnosis. Only a doctor can do that; when to go to your GP is set out below.

How often a bloated belly occurs

In a Rome Foundation study among 51,425 people in 26 countries, almost 18 percent had a bloated belly at least once a week, for three months. Women reported it about twice as often as men, and the complaint became less common with age. Of those who had abdominal pain weekly, more than six in ten also had a bloated belly.⁠²

It rarely stands on its own: in the same study, more than 40 percent of the online participants met the criteria for at least one functional stomach or bowel complaint.⁠³ The best known is irritable bowel syndrome, which about one in 25 people in the Netherlands has.⁠⁴

Why your belly expands, even without extra gas

The picture of a balloon filling up is usually wrong. Back in 1975, researchers measured how much gas sat in the gut of twelve people with chronic gas complaints: 176 millilitres on average, against 199 millilitres in ten people without complaints. No difference. What did differ: in those who developed pain, the gas took longer to pass, and the same amount hurt more.⁠¹

Where the swollen belly does come from was shown by scans. In 56 people whose main complaint was a bloated belly, a CT scan was made at rest and during a severe episode. With a functional bowel complaint the contents of the abdomen barely increased, by 0.3 litres, while the abdominal wall came forward by 14 millimetres: the diaphragm dropped and pushed the contents forward.⁠⁵ In a follow-up study, twenty people with this complaint and fifteen without were given the same amount of gas in the gut; in the people with complaints the diaphragm contracted instead of relaxing, and their belly expanded more.⁠⁶

A bloated feeling and a belly that measurably gets bigger are also two different things, and they often occur together.⁠⁷

What food has to do with it

For some people, food does a lot. In a controlled study, thirty people with irritable bowel syndrome ate a diet low in fermentable carbohydrates for three weeks and an ordinary Australian diet for three weeks. Their symptom score was 22.8 on the first diet and 44.9 on the second, on a scale of 100; in healthy people the diet did nothing.⁠⁸ A diet like that is work for a dietitian, but it shows that what you eat plays a measurable part.

What a gut scan measures

The gut scan asks six questions about the past few weeks: the form of your stools, belly pain or discomfort, a bloated feeling, how regularly you go, reflux or heartburn, and complaints after certain foods. Each question is given points, the points are added up and converted into a gut score from 0 to 100, with the reading band it falls into. Higher is better.

The questions are modelled on two validated symptom scales. The Bristol Stool Form Scale reads the form of your stools as a signal of how fast your gut works: in 66 volunteers, the form matched the measured transit time more closely than how often they went.⁠⁹ The Gastrointestinal Symptom Rating Scale rates stomach and gut complaints with fifteen questions, and that set-up is our model.⁠¹⁰ The questions about pain and food follow how the Rome IV criteria describe the pattern of complaints, only to describe your pattern and never to establish anything.⁠¹¹ Our questions are written by us, not a copy, so the score is not a validated clinical score. What you get is a structured picture of your symptom load and a starting value.

What a gut scan does not measure

A questionnaire reads the load you describe. It cannot see whether this is irritable bowel syndrome, an intolerance, coeliac disease or something that clears up on its own. That needs a doctor, and sometimes blood or stool tests. So a gut scan does not make a diagnosis. A low score means that looking further makes sense, and nothing more.

Your GP asks questions and examines your abdomen; tests at the hospital are usually not needed. Three things are a reason to make an appointment: blood on or in your stools, your weight going down without you knowing why, and getting bowel complaints for the first time when you are 50 or older.⁠⁴

What you do with your score

Most people start by cutting things out: first the bread, then the onion, then the milk. A month later you still do not know whether it did anything, because you never wrote down where you started. A score from today is that starting value. Repeat the scan a few weeks later, on the same questions, and you have two numbers instead of a feeling.

If you want to do something in those weeks, write down when your belly swells up and what you ate that day: that is what a GP or dietitian can work with.