Bloating? Here's What's Going On

Good morning!

So here’s a question… do you know what bloating is? Maybe it's a stomach that feels uncomfortably full after dinner, a waistband that seems to get tighter as the day goes on, or that familiar feeling that your digestive system has simply decided to cause problems.

The frustrating part is that bloating isn't a single condition with a single cause. Gas, constipation, food intolerance, changes in gut movement, and even the way your digestive system responds to certain foods can all produce that same uncomfortable feeling. That's why the usual advice (like drink more water, cut out dairy, take a probiotic) can work brilliantly for one person and do absolutely nothing for another.

This week, I’m breaking down what bloating is, and why it happens.

Key Takeaways

• Bloating can have different causes, including food fermentation, gut sensitivity, slowed motility, and hormonal changes.

• The best solution depends on the cause. There's no single food, supplement, or diet that works for every type of bloating.

• For most healthy people, bloating is uncomfortable but not dangerous. Knowing when it warrants attention versus when it's simply a signal worth understanding makes the whole thing significantly less stressful.

CORE

(Too Much) Fermentation

This is probably the cause most people think of when they hear the word "bloating," and it's also the reason so much dietary advice focuses on eliminating certain foods. The basic process is fairly simple. When carbohydrates aren't fully absorbed in the small intestine, they continue into the colon, where gut bacteria ferment them. Gas is produced as a byproduct, and that extra gas can leave you feeling distended, uncomfortable, and ready to unbutton your jeans.

Many of the carbohydrates that cause this are grouped under the acronym FODMAPs, a complicated name for a fairly recognizable collection of carbohydrates. They include lactose in dairy, fructose in certain fruits and sweeteners, fructans found in foods like wheat, onions, and garlic, and galacto-oligosaccharides found in legumes and beans. Not everyone reacts to all of them. Your individual digestive capacity and gut microbiome help determine which foods cause problems and which ones don't.

There's another culprit that's particularly easy to miss, sugar alcohols. They're commonly added to sugar-free products, protein bars, and chewing gum, often under names like sorbitol, xylitol, and other "-itol" sweeteners. These compounds can draw additional water into the intestine while also being fermented by gut bacteria, creating a combination of fluid and gas that can contribute to bloating and abdominal distension. 

For people dealing with persistent bloating, another possibility is small intestinal bacterial overgrowth (SIBO), where excessive bacteria in the small intestine ferment carbohydrates earlier in the digestive process than they normally would (we wrote a newsletter on this here!). This can produce gas and bloating, particularly after meals, although SIBO is only one potential explanation for chronic symptoms and shouldn't be assumed to be the cause without proper evaluation.

Hypersensitivity

Not all bloating comes from having too much gas. In some people, the problem is that the gut becomes more sensitive to normal amounts of gas, food, or intestinal movement, making sensations that would normally go unnoticed feel uncomfortable or even painful.

Your gut has its own nervous system, called the enteric nervous system (read our edition on this here), which constantly communicates with your brain. When this system becomes hypersensitive, normal digestive activity can be interpreted as pressure, fullness, or distension, even when there isn't actually an unusual amount of gas in the intestine. This is known as visceral hypersensitivity and is a common feature of irritable bowel syndrome, although it can occur without an IBS diagnosis.

This distinction matters because it changes what might actually help. If your bloating is being driven by an overly sensitive gut rather than excess fermentation, eliminating more foods or adding another probiotic may not address the underlying problem. Gut-directed hypnotherapy, stress reduction, and, in some cases, medications that influence gut-brain signaling have evidence for helping calm this heightened sensitivity.

Gut Motility

Another common cause of bloating has less to do with what you eat and more to do with how quickly your digestive system moves it along. Gut motility refers to the speed at which food and waste move through the digestive system, and it has a significant effect on how much gas accumulates and how long it sits there.

When transit slows, due to dehydration, low fiber intake, sedentary habits, or hormonal changes (such as the rise of progesterone, which slow gut mobility), stool sits in the colon longer, fermentation time increases, and the gut feels fuller and more pressurized. When stool sits in the colon longer, it becomes drier and harder to pass, with more time for fermentation and gas production, and the bowel can feel fuller.

Stress and poor sleep also impair motility independently, through their effects on the gut-brain axis, which is why bloating often worsens during stressful periods even without any change in diet.

How Should You Deal With Bloating?

This is the thread that ties all the mentioned causes together, and it's the most practically useful takeaway from the research.

Bloating is consistently treated as though it's one condition with one solution, cut out X food, take Y supplement. But if fermentation-driven bloating responds to a low-FODMAP diet, visceral hypersensitivity doesn't, motility issues need a different approach entirely, and the muscular coordination problem isn't addressed by any of them, then the reason generic advice works brilliantly for some people and does nothing for others isn't mysterious. They're treating different problems.

That's why paying attention to the pattern matters. If bloating reliably follows certain foods, fermentation may be playing a role. If it happens regardless of what you eat, gut sensitivity or motility could be more relevant. And if it consistently gets worse during periods of stress, the gut-brain connection may be part of the picture.

The answer shapes the approach, and explains why the same trial-and-error process that took one person a week to solve has taken another person years without resolution.

ENDNOTE

Final Thoughts

One last quick but important note, for most people, bloating is a functional digestive issue, not a sign that something dangerous is happening. It's real, it can be uncomfortable, and it can absolutely interfere with your day, but feeling bloated doesn't automatically mean something is wrong with your digestive system.

That said, some symptoms deserve more attention. Bloating that is persistent, progressively worsening, or accompanied by unintentional weight loss, blood in the stool, or significant pain is worth discussing with your doctor.

Until next week!

Adrian Macdonald | Team Dietitian | The 8% Newsletter Author