Intermittent fasting may actually increase the risk of developing cancer

Intermittent fasting, an increasingly popular practice, might have unexpected health consequences.

A new study conducted on mice by researchers at the Massachusetts Institute of Technology (MIT) reveals that while it promotes the regeneration of intestinal cells, this type of fasting might also increase the risk of intestinal cancer.


Nature recently published the results of this study, showing that intermittent fasting activates the regenerative capacity of intestinal stem cells, thus enabling the intestine to recover from injuries or inflammation. However, the researchers also observed an increased risk of developing intestinal tumors in mice, particularly when cancerous mutations occur during the cell regeneration phase following fasting.

To understand these mechanisms, the research team, led by Omer Yilmaz, a biology professor at MIT, studied three groups of mice: one group fasted throughout the study period, another fasted for 24 hours followed by a refeeding period, and a control group that ate freely throughout the experiment. The results showed that intestinal stem cells proliferated more at the end of the refeeding period compared to the cells of mice that did not fast.

The researchers identified that this increased regeneration is due to the activation of a cell signaling pathway known as mTOR, which is involved in cell growth and metabolism. During the refeeding phase, this pathway leads to an increased production of polyamines, small molecules that promote cell growth and division. However, this intense regenerative activity could facilitate the development of precancerous cells.

During this refeeding phase, mice with cancerous mutations showed a higher risk of developing precancerous polyps compared to those that remained fasting or did not undergo a fasting and refeeding cycle. According to Omer Yilmaz, although these results are limited to animal models, they suggest that the period following fasting, combined with exposure to mutagens like grilled meat, could increase the risk of developing cancerous lesions.

The study suggests that while intermittent fasting presents health benefits, it could also carry risks, especially for individuals exposed to potentially carcinogenic substances during the refeeding period. Researchers continue their work to better understand how to leverage the beneficial effects of fasting while minimizing potential risks.