A new study shows neurons in mice that influence metabolism are active for up to two days after a single workout. The  study , published in the journal  Molecular Metabolism , offers new insight into the brain's potential role in fitness and may provide a target for developing therapies that improve metabolism.

"It does not take much exercise to alter the activity of these neurons," said Dr. Kevin Williams. "Based on our results, we would predict that getting out and exercising even once in a semi-intense manner can reap benefits that can last for days, in particular with respect to glucose metabolism."

In the study, Dr. Williams and co-authors measured the effects of short- and long-term exercise on two types of neurons that comprise the melanocortin brain circuit, which is shared by both humans and mice.

One of the neuron types – Pro-opiomelanocortin (POMC) neurons – is associated with reduced appetite, lower blood glucose levels, and higher energy burning when activated; the other type – Neuropeptide Y / Agouti-Related Peptide (NPY / AgRP) neurons – increases appetite and diminishes metabolism when activated.

The study found that a single bout of exercise can boost the activity of POMC neurons and inhibit the counterpart NPY / AgRP neuron for up to two days. Those changes last longer with more training.

The findings expand the scientific understanding of the melanocortin circuit, which previous studies showed could be altered through feeding or fasting but had not been linked to exercise, they also provide another avenue to research potential treatments to improve glucose metabolism in patients with conditions such as diabetes.

Brain circuit activity 

The scientists measured brain circuit activity in mice given training regiments that lasted from zero to 10 days. They found that a single workout – consisting of three 20-minute treadmill runs – caused a decrease in appetite that lasted up to six hours.

"This result may explain at the neural circuit level why many people do not feel hungry immediately after exercise," Dr. Williams said. The longer-term effects of exercise were seen in the POMC neurons, which improve glucose metabolism when activated.

These neurons remained active longer if they also expressed a protein called the receptor leptin"Our research is not just for improving fitness. A better understanding of neural links to exercise can potentially help a number of conditions affected by glucose regulation, "Dr. Williams said.