Antibiotics Can Ruin Your Motivation and Endurance

According to recent research, antibiotics can also ruin athletic performance.

Eliminating gut microorganisms reduces motivation and ability to exercise.

According to a recent study, antibiotics destroy essential gut bacteria, which destroys athletes’ motivation and endurance. According to a mouse study conducted by the University of California, Riverside, a significant element differentiating athletes from couch potatoes is their microbiome.

This study is one of few that looks at how gut bacteria also influence voluntary exercise habits. While other studies have looked at how exercise impacts the microbiome, this one looks at the opposite. Both athletic prowess and motivation are required for voluntary exercise.

The researchers’ results were recently published in the journal Behavioural Processes.

Aerobic Plates: 10 days of antibiotics reduced the adult gut microbiome from millions of aerobic colony-forming units to a non-detectable amount. Credit: Monica McNamara/UCR

“We believed an animal’s collection of gut bacteria, its microbiome, would affect digestive processes and muscle function, as well as motivation for various behaviors, including exercise,” said Theodore Garland, UCR evolutionary physiologist in whose lab the research was conducted. “Our study reinforces this belief.”

Researchers used fecal samples to demonstrate that, after 10 days of antibiotic treatment, the gut bacteria of two groups of mice—those bred for high levels of running, and some that were not—were reduced.

Both mouse groups showed no symptoms of illness after the antibiotic therapy. Researchers were thus convinced that the microbiota damage was to blame when wheel running in the athletic mice was decreased by 21%. The high runner mice also failed to recover their running behaviors 12 days after the antibiotic treatment was terminated.

Both during and after the treatment, the behavior of the normal mice was not significantly changed.

Lead author Monica McNamara counting anaerobic plates. Credit: Monica McNamara/UCR

“A casual exerciser with a minor injury wouldn’t be affected much. But on a world-class athlete, a small setback can be much more magnified,” said Monica McNamara, UCR evolutionary biology doctoral student, and the paper’s first author. “That’s why we wanted to compare the two types of mice.” Knocking out the normal gut microbiome might be compared with an injury.

One way the microbiome might affect exercise in mice or in humans is through its ability to transform carbohydrates into chemicals that travel through the body and affect muscle performance.

“Metabolic end products from bacteria in the gut can be reabsorbed and used as fuel,” Garland said. “Fewer good bacteria means less available fuel.”

Moving forward, the researchers would like to identify the specific bacteria responsible for increased athletic performance. “If we can pinpoint the right microbes, there exists the possibility of using them as a therapeutic to help average people exercise more,” Garland said.

A lack of exercise is known to be a major risk factor for aspects of mental health, including depression, as well as physical health, including metabolic syndrome, diabetes, obesity, cardiovascular disease, cancer, and osteoporosis. Many in the public health community would like to promote exercise, but few have found ways to do it successfully.

“Though we are studying mice, their physiology is very similar to humans. The more we learn from them, the better our chances of improving our own health,” Garland said.

Certain foods may also increase desirable gut bacteria. While research into “probiotics” is developing, Garland recommends that those interested in promoting overall health maintain a balanced diet in addition to regular exercise.

“We do know from previous studies that the western diet, high in fat and sugar, can have a negative effect on biodiversity in your gut and likely, by extension, on athletic ability and possibly even on motivation to exercise,” Garland said.

Reference: “Oral antibiotics reduce voluntary exercise behavior in athletic mice” by Monica P. McNamara, Marcell D. Cadney, Alberto A.Castro, David A. Hillis, Kelly M. Kallini, John C. Macbeth, Margaret P. Schmill, Nicole E. Schwartz, Ansel Hsiao and Theodore Garland Jr., 4 May 2022, Behavioural Processes.
DOI: 10.1016/j.beproc.2022.104650