My gut made me exercise

Many of us, when we reach a certain age, look down at our bodies and vow to make a change. We want to get thinner or become healthier, so we start an exercise program and hope it will extend for more than a few weeks. Our change in behaviour is a conscious act of will, we think, aimed at correcting a specific problem.

For part of my research career, I studied exercise in rats by looking at wheel running. These wheels are a more substantial version of the kind you can purchase in a pet store for small rodents. They are made of metal bars and have a diameter of about 30 centimetres. Rats can enter the wheel, run, and cause the wheel to rotate. How much an animal runs in these wheels varies considerably. Some rats run over 15 kilometres a night (their active period), while others run only a few hundred metres (one wheel rotation is about a metre). As you might expect, rats that run more in the wheel weigh less and are healthier than rats that don’t run.

Fast microbes

Last December, in Nature, researchers reported on a different factor that can influence exercise: the gut. They found that in mice, there was a biological gut-brain connection that determined how much mice ran. The mix of microbes in the gut was correlated with the amount of running. To test this relationship experimentally, the researchers gave antibiotics (which kill the microbes) to the high-running mice, and the amount of running decreased. Introducing the gut microbes of high runners into mice without microbes led to increases in the recipients’ running to levels found in the donor mice. More research showed these microbes influence dopamine levels (the neurotransmitter in the brain associated with pleasure), so it seems that elevated dopamine activity led to more running (note that I am leaving out a lot of the details).

While mice studies often do not translate to humans, we are learning more about how microbes and bacteria in our intestines affect our health and behaviour. It would not be surprising if similar interactions between our gut microbes and exercise might exist in humans. If, in humans, the particulars of the gut microbes influence brain neurotransmitters like dopamine, then potential treatments become possible for various human conditions that affect our behaviour and mood. Your gut may directly influence how much you want to exercise.

Wonderfully made

This interconnection highlights that our Lord has made us integrated individuals. We are not separate brain and body, or mind, heart and soul. Instead, we are one person, and all our parts work together to make us who we are. We cannot treat each piece separately but must view any treatment as acting on the whole individual. As scripture says and science shows again and again, we are wonderfully made.