Not Motivated to Exercise? Your Gut Microbes May Be to Blame

When we think of the treadmill, it rarely has a good connotation. But while it might imply tedium to a human, it is rejuvenating to a mouse. Exercise and a proper diet are the two most important things we can do for our physical and mental health. Being couch potatoes is surprisingly damaging to our well-being. Evolution has not properly prepared us for bingeing on Netflix.

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But how do we motivate ourselves to get off our butts and into our running shorts? Exercise involves our muscles, heart, lung, and, surprisingly, our guts. An intriguing connection between exercise and diet goes straight through the collection of microbes in our gut called the microbiota.

Microbes and Neurotransmitters

A recent study by Christoph Thaiss and colleagues at the University of Pennsylvania found that certain microbes in mice can produce endocannabinoids, the body’s own version of cannabis. The endocannabinoid system is a surprisingly complex cell-signaling system involved in energy balance, among other things. It also elevates dopamine levels in a part of the brain called the ventral striatum during exercise, which increases the mouse’s inclination to exercise as well as its performance.

Germ-free mice raised in a sterile environment do not exercise as long or as well as normal germy mice, and when antibiotics are delivered to kill off gut microbes, the exercise effect disappears. The researchers concluded that the microbiota influences the rewarding properties of exercise, like runner’s high. Because microbes are different for each animal, this also explains at least some of the individual variability in performance.

The researchers said, “If applicable to humans, our findings imply that [chemicals] that stimulate the motivation for exercise might present a powerful opportunity to counteract the detrimental health impact of a sedentary lifestyle.”

How about humans?

Not all mouse studies are relevant to humans, but both mice and people have a similar endocannabinoid system connected to the ventral striatum. We also know that there is a connection between exercise, microbes, and metabolism. In a brilliant, if somewhat unsavory, experiment, Chun-Ying Wu and colleagues at Taichung Veterans General Hospital in Taiwan showed that metabolic profiles of athletic mice could be transferred to overweight mice on a high-fat diet.

How do you transfer a microbiota? Via fecal transplant. This is not troubling to a mouse, as they eat each other’s droppings all the time. But it is remarkable that a fat, sedentary mouse can get a supercharged metabolism from the poop of a champion wheel runner. This demonstrates that the effect is not just correlational but causal. The beneficiaries of these fecal transplants lose weight, gain strength, and are more motivated to exercise.

What to do?

What can we do to encourage us to quit hogging the sofa? Besides endocannabinoids and dopamine, GABA is another neurotransmitter that plays a role in our health, reducing pain and anxiety, factors that make us less likely to exercise. Certain species of Lactobacillus and Bifidobacteria produce GABA, and they are easy to find in fermented foods like yogurt. So, introducing ferments into the diet may give us a little nudge in the right direction.

As well as microbes affecting our motivation to exercise, we know that exercise can improve our microbiota, thereby boosting our moods. This circularity of the microbiota is not uncommon, and it provides us with another lever to control our exercise regimens.

If we can break the will of our recalcitrant gut microbes and use the treadmill for more than hanging clothes, we quickly benefit. Exercise lowers levels of pathogenic bacteria and increases their overall diversity – a good thing.

Among the bacteria to benefit from exercise are Clostridiales, Roseburia, Lachnospiraceae, and Erysipelotrichaceae. These microbes secrete short-chain fatty acids like butyrate, which both heal and nourish the gut lining. Extreme exercise, however, often leads to a leaky gut and systemic inflammation. This is partly due to a redirection of blood flow away from the gut in favor of skeletal muscle. Athletes at this elite level often complain of intestinal distress. Fortunately, these effects are short-termed, and athletes, in general, have a better, more diverse set of microbes that are resilient to disease and inflammation.

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So, a better diet can build a better microbiota that can help us boost our motivation to exercise. And then, once we start to exercise, we might be able to further improve that microbiota in a virtuous cycle. That is an easy way to break the curse of sofa squatting and set us on a path to better health and a happier mood.