There’s nothing worse than spending hours at the gym slogging your guts out, only to feel as though you’re not making much progress. You might be progressively overloading your key moves, getting a decent sleep most nights and eating well but still not see great returns on your investment. 

The missing key – the one that just about impacts every part of our physical and mental health – may be gut health. If you’re someone who struggles with bloating, sluggishness, non-regular loo habits, then it’s time to see if your gut microbiome is actively usurping your efforts to get fitter. 

Lower levels of nutrient absorption 

“The gut plays a vital role in absorption and utilisation of essential nutrients that are needed all around the body for many different functions. This can include energy production and metabolism,” explains allplants’ nutritionist Ally Findlay. 

We all know that nutrition plays a big part in athletic performance and “with a weakened or unhealthy gut, you’re less able to fully absorb the nutrients in the food you consume, which could have a knock-on effect on your progress and health in general.” 

Increased inflammation

Of course, it’s not just that poor gut health can make us weaker; doing too much intense exercise can weaken out guts. According to Michelle den Hollander, nutritionist and hormone expert, lots of intense exercise can cause the body to release hormones that promote the growth of “bad” bacteria and other inflammation-promoting substances. 

“If you are training intensively, you may also experience a ‘leaky gut’ where the intestinal lining opens up, making room for bad bacteria to leave the intestinal canal and start moving around your body. This compromises the immune system significantly and needs to be treated as soon as possible.” 

The key, she says, is to listen to your body as you know your body best. “By ignoring signs like a bloated belly or pain, you can make things worse. So if any of these symptoms happen regularly, reduce your exercise impact or take a day off and if it disappears and does not come back then continue.”

Risk of constipation

Another factor, when it comes to exercise, is dehydration. If you don’t come up with a plan for taking on fluids on a long run or commit to rehydrating once you finish your work out, you might run into further digestive issues. 

Findlay explains that the large intestine soaks up the water it has access to, making your digestion slow down – resulting in constipation. If you are experiencing gut related problems when exercising, Findlay says that “there is likely another factor involved and it is worth checking in with your doctor.”

Increased discomfort

den Hollander warns: “Bloating and inflammation will definitely get in the way of training and thus hinder you from your fitness goals. Gut health is often underestimated when, in fact, it’s a big factor to consider when you want to get fit.” 

If you’re used to feeling bloated during or after a run, you might be tempted to change how and when you fuel. While the timing of when you eat won’t impact your gut health itself, food can get in the way during training if you leave too little time between a meal and a workout. Choose an easily digestible snack like a banana or bread and nut butter before a workout but give yourself an hour between a meal and movement.

Slower lactic acid clearance 

den Hollander explains that our gut not only helps with digestion, it also plays a role in our metabolism, immune and hormonal system and even our cognitive functions – all of which affect our physical performance.

 “It has also been proven that our gut breaks down lactic acid that is needed to build up muscles, so if your gut health is poor it won’t be able to work effectively to help your strength and muscles grow.”

Our guts are always busy. If they’re not absorbing nutrients to keep us nourished, energised and strong, they’re supporting the immune system. A “healthy” gut has a rich array of gut microbiota (the millions of microorganisms within your digestive tract) so that it can carry out all of its functions properly. That means having lots of different kinds of bacteria; the more diverse the microbiota, the stronger the gut.


There are lots of factors that lead to poor gut health, including:

• High-stress levels (emotional and physical)
• A diet high in processed and refined foods (especially foods containing lots of additives and preservatives)
• Too much exposure to antibiotics or other drugs

Given how important our guts are, it’s pretty noticeable when things go wrong. Common symptoms to look out for are bloating and gas, which Findlay says “can signal high levels of bad gut bacteria”. 

Food intolerances can also be a sign that the gut is not functioning correctly; you may not be able to break down food correctly and that causes reactions in the body. Oh, and because gut bacteria is linked to the immune systems, gut problems can negatively impact immune health too.  

Research shows that regular aerobic exercise can actually beneficially change your gut bacteria and microbiome. 

A 2019 study published in the journal Experimental Physiology concluded that those people with higher cardiorespiratory fitness tend to have a more diverse bacterial population in the gut, compared with those with a lower level of cardio fitness.

Another study found that exercise promotes the growth of bacteria which produce the fatty acid, butyrate. Butyrate is thought to reduce inflammation (reducing the risk of issues like inflammatory bowel disease and insulin resistance), as well as help to heal the gut lining. But you don’t have to do HIIT or sprints to reap the gut benefits. The same paper found that women who do at least three hours of light exercise (such as a brisk walk) per week have been found to have increased levels of anti-inflammatory bacterias compared with more sedentary individuals. 

If you’re a runner or cyclist, you’ve got a reason to feel good: researchers have shown runners and cyclists produce more endocannabinoids in their blood, which provides some pain relief and improves mood. Endocannabinoids are involved in controlling gut inflammation and protecting our gut barrier. What’s not yet been established, however, is how short-lived these changes are or whether that boost can lead to long-term changes in the gut microbiome. 

Given that “runner’s stomach” is such a thing (ask anyone who’s trained for a long-distance event and they’ll tell you that their guts have become incredibly sensitive), however, surely there’s a limit to how much movement is good for a gut?

Our digestive systems may be able to handle a lot but ultimately, they aren’t designed to experience the kind of incessant stress that hours of running can create. When we run or engage in lots of high-intensity activity, our blood flow moves away from the digestive system to the cardiovascular system. That then can trigger an inflammatory response in the gut. 

1. Eat the rainbow

Water is a key component of digestion and ensures the proper absorption of nutrients. Water also keeps food moving through the intestines. If you don’t have enough water in your body, water is reabsorbed from the colon often leading to hard stools and constipation. 

Images: Getty