Dr Orange, a senior lecturer in clinical exercise physiology, said it showed “even a single workout” could make a difference.
“What’s remarkable is that exercise doesn’t just benefit healthy tissues, it sends powerful signals through the bloodstream that can directly influence thousands of genes in cancer cells,” he said.
The research team said their finding offered a “potential mechanistic explanation for the protective effects of exercise” against bowel cancer.
Genevieve Edwards, chief executive at the charity Bowel Cancer UK, said people should aim for 150 minutes of exercise each week, such as brisk walking, cycling or swimming.
Eating fibre from whole grains, pulses, fruits and vegetables, avoiding processed meat and cutting down on alcohol also reduced the risk.
She added: “Making lifestyle changes can be a challenge, but we believe it’s worth the effort.”