Key points from article :
A new study led by Rachel Perry from Yale School of Medicine, and published in PNAS offers fresh insight into how exercise may slow cancer growth. While it’s long been known that regular physical activity lowers cancer risk and improves survival, this research uncovers a metabolic mechanism that helps explain why.
Perry’s team injected breast cancer cells into mice—some lean, some obese—and allowed half of them to exercise voluntarily on a running wheel. After four weeks, obese mice that exercised had tumours 60% smaller than obese sedentary mice, and even lean sedentary mice showed slightly larger tumours than the active group. A single 30-minute workout shifted oxygen and glucose uptake toward the muscles and away from the tumours, meaning muscle cells effectively “outcompeted” cancer cells for their main fuel.
Gene-activity analyses identified 417 genes involved in metabolism that changed in response to exercise, boosting glucose use in muscle and reducing it within tumours. The researchers also found reduced activity of mTOR, a growth-promoting protein in cancer cells, which may further suppress tumour expansion. Because these metabolic pathways are highly conserved across mammals, the team expects the same effect to occur in humans—and early evidence suggests this is already happening.
Experts say the results reinforce the idea that exercise creates a cancer-suppressive environment. The findings also help explain why low muscle mass is tied to worse cancer outcomes: more active muscle means stronger competition for glucose. The researchers argue that exercise should be considered a genuine adjunct cancer therapy, with personalised approaches—such as cardio to boost fitness or resistance training to build muscle—depending on each patient’s needs.
