Why does my stomach bloat in hot weather?

What causes bloating?

It's normal for your stomach to swell and flatten in a cycle, as the food and drink you consume reaches your gut (also called the gastrointestinal tract) and is digested. This activity contributes to a daily pattern that shouldn't normally cause you discomfort or pain.

Sometimes, noticeable abdominal bloating - when your stomach feels particularly stretched and swollen - occurs when your gut becomes filled with excess air or gas. Usually this is temporary and nothing to worry about, although bloating can be accompanied by other symptoms, ranging from the mildly annoying to the painful:

These include:

• Stomach pain or discomfort.

• Stomach rumbling or gurgles.

• Excessive gas (flatulence).

• Frequent burping.

A lot of the time, this happens when you consume certain foods or drinks that can cause excess gas, but other lifestyle factors, such as how well you're sleeping and your stress levels, can also affect your digestive health.

Why you feel bloated in hot weather

If you find yourself feeling more bloated in hot weather, it's a good idea to look at the lifestyle factors that are influenced by the heat. Let's take a look at some of the most common summer habits that may be causing your stomach to swell.

Dehydration

We all know that we should drink more water when it's hot. This is because our bodies lose more water content and essential minerals (electrolytes) than usual through sweating¹, which in turn may trigger you to become bloated in hot weather (through a process known as water retention).

According to Kirsten Jackson, consultant dietitian at The Food Treatment Clinic and British Dietetic Association (BDA) member, our tendency to gulp water when we're dehydrated can also lead to more gas and bloating because we swallow more air.

Dehydration can be serious and on a hot day may result in heatstroke. Keep a water bottle with you and look out for the common signs:

• Thirst.

• Urinating (needing to wee) less frequently.

• Yellow and dark yellow urine.

• Fatigue.

• Dry mouth.

• Light-headedness and dizziness.

• Confusion.

• Increased heart rate and breathing.

Summer foods

It could be that your favourite summer foods are to blame. "An overload of certain foods, such as ice cream which is high in fructose (a type of sugar), could be having an impact," says Jackson.

"During the summer, people may also increase their intake of raw vegetables and light salads as they are cooling and refreshing. However, this increase in fibre may cause bloating for some people. I always advise increasing your fibre intake gradually² while drinking more fluids to avoid constipation and bloating."

Common triggers:

• Sweet snacks like ice cream and lollies.

• Lettuce.

• Tomatoes.

• Carrots.

Summer drinks

Bad news for the summertime boozers: your go-to summer cocktail, pub garden beer, or trendy rooftop hard seltzer could be responsible for your summer swell. Alcohol is inflammatory, meaning that it irritates your gut which can cause bloating.

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Many of us enjoy an ice-cold fizzy drink in the summer sun, but these can also leave you feeling bloated. Fizzy drinks are carbonated, meaning that gas is blended with the liquid to create the fizziness we find so refreshing in the heat. Unfortunately, this gas tends to puff out the stomach.

It stands to reason that a summer drink that's both alcoholic and fizzy is the perfect cocktail for being bloated in hot weather. It's a sad fact that so many popular summer drinks tick both boxes.

Common triggers:

• Beer.

• Cocktails - especially sweet ones that are high in fructose.

• Spirits served with fizzy drink mixers.

• Fizzy drinks - including Coca-Cola, Sprite, and Fanta.

Disturbed sleep

"Sleep can be interrupted in the summer, due to it being so hot at night, which can lead to gut symptoms such as bloating," explains Jackson.

A lack of good-quality sleep can affect your gut health in several ways:

• It can increase stress - lack of sleep increases production of cortisol, otherwise known as the 'stress hormone'³. Increased stress can cause food and toxins to pass through the intestinal wall into the bloodstream, leading to bloating among other symptoms.

• It influences your dietary choices - feeling tired causes you to crave food that will give you a quick energy boost⁴. This tends to lead us to lots of sugar and trans fats - ingredients that can cause gut inflammation.

• It can encourage late-night eating - staying up late into the night makes you more likely to snack before bed, but your metabolism slows down at night which means that this food won't be properly digested as you sleep. The result is often a swollen stomach in the morning.

A stretched stomach can make you feel uncomfortable and self-conscious, which can be particularly hard when you're bloated in hot weather on a summer's day. You can always opt for looser-fitting clothes that are also lightweight, as tight garments can press on your tummy and cause further discomfort or indigestion cramps.

Remember though, the chances are no one else has noticed your bloat! The best way to enjoy your summer is to stay hydrated, to eat healthily, and not to stress about how any temporary tummy bulges look.

Further reading

1. Johns Hopkins Medicine, "Dehydration and heat stroke".

2. Fathallah et al. "Diet and lifestyle rules in chronic constipation in adults: From fantasy to reality".

3. The Sleep Doctor, "Cortisol and sleep".

4. Greer et al. "The impact of sleep deprivation on food desire in the human brain".