Don't want to exercise? It turns out you can blame your intestinal flora

Looking at the fitness and marathon masters in my circle of friends showing off their muscles and showing their pace, and then looking at myself being extremely lazy, not to mention exercising, I would rather lie down than sit, I can't help but sigh: How can the gap between people be so big?

However, the latest scientific research has given a new explanation to the majority of lazy people who don’t like to exercise. It turns out that it’s not that I don’t like to exercise, but that I am controlled by my intestinal flora. It’s it... it it it it it that doesn’t let me move!

Researchers from the Perelman School of Medicine at the University of Pennsylvania found in experiments with mice that changing the structure of the intestinal flora would also change the mice's interest in exercise. After taking antibiotics, the healthy mice that originally liked to exercise in a treadmill lost most of their intestinal flora, and the mice no longer wanted to exercise. Scientists also found several strains of bacteria that promote mouse exercise, mainly strains of the Erysipelothrix family and the Lachnospiraceae family. After supplementing the germ-free mice with these strains of bacteria, the mice exercised for longer periods of time and more frequently [1].

Figure 1. A hamster exercising

What controls our willingness to exercise? And how does our gut flora determine whether we want to exercise?

The area of ​​the brain responsible for the desire to exercise is the striatum, and the neurotransmitters that regulate whether the striatum is excited or not include dopamine, acetylcholine, and glutamate. There is a positive feedback between dopamine and exercise. Exercise can produce dopamine, which excites the striatum and makes the desire to exercise stronger. However, when the intestinal flora is destroyed, the dopamine produced by the mouse during exercise decreases significantly. Without the motivation and positive feedback of dopamine, the mouse striatum is no longer excited and loses the motivation to exercise.

How does the positive feedback between dopamine and exercise end? The more you exercise, the more dopamine you produce. The more you want to exercise, the more tired you will be. Fortunately, dopamine has a short half-life. When the striatum of the brain is stimulated by dopamine, it will produce monoamine oxidase that decomposes dopamine, so dopamine does not accumulate in the brain. However, the presence of intestinal flora will inhibit the decomposition of dopamine by monoamine oxidase, delay the decomposition of dopamine, and the feeling of reward from exercise will be stronger.

Figure 2. The striatum (red) in the brain is responsible for movement and reward mechanisms

In addition, some bacteria in the intestines, such as Coprococcus of the Erysipelothrix family and the Lachnospiraceae family, can synthesize fatty acid amides . This metabolite excites sensory neurons, causing mice to release more dopamine during exercise and feel more rewarded and happy.

In fact, this is not the first time that scientists have discovered the connection between intestinal flora and exercise. In addition to regulating the willingness to exercise, intestinal flora also participates in the utilization of metabolites during exercise and is even related to changes in muscle structure or content.

In 2019, Professor George M. Church of Harvard Medical School and his team published an article in Nature Medicine, comparing the composition of intestinal flora of marathon runners and their sedentary peers. Researchers found that there was a strain of Veillonella in the intestines of marathon runners, and the number increased significantly after long-distance running. Transplanting this type of bacteria into the intestines of mice allowed the mice to run longer on the wheel and gain the same endurance as marathon runners [2], indicating that these strains of Veillonella are related to the endurance and exercise duration of athletes.

The reason why the content of this type of bacteria increases after marathon runners is because they are good at metabolizing lactic acid produced by exercise. They break down lactic acid into propionate, which returns to the athlete's muscle cells and participates in the energy metabolism process of muscle cells. I didn't expect that the intestinal flora would not be idle during our running and could help a little.

Although the above scientific research results are only found in mouse exercise models, considering various factors such as individual differences, willpower, training methods, etc., the improvement of intestinal flora on exercise willingness or fitness effect may not be particularly obvious. However, the above article provides us with new ideas to promote exercise. For example, can fatty acid amides be added to the diet to enhance exercise willingness? Or add strains such as Coprococcus and Veillonella that can help exercise metabolism to probiotic products to make exercise more pleasant and lasting? I hope to see the emergence of relevant clinical research one day, which will surely help and motivate patients with obesity, metabolic diseases or "late-stage lazy cancer" to do more physical exercise and improve their body shape and physical condition.

But before that day comes, you can't give up on yourself. Start exercising regularly from today and synthesize dopamine through your own efforts!

References

1. Dohnalová, L., Lundgren, P., Carty, JRE et al. A microbiome-dependent gut–brain pathway regulates motivation for exercise. Nature 612, 739–747 (2022).

2. ScheimanJ, Luber JM, Chavkin TA, MacDonald T, Tung A, Pham LD, Wibowo MC, Wurth RC, Punthambaker S, Tierney BT, Yang Z, Hattab MW, Avila-Pacheco J, Clish CB, Lessard S, Church GM, Kostic AD. Meta-omics analysis of elite athletes identifies a performance-enhancing microbe that functions via lactatemetabolism. Nat Med. 2019 Jul;25(7):1104-1109.

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