Over the years, lots of studies have hinted that intermittent fasting might be good for our health and even lower cancer risks. But a recent study in mice suggests it could actually increase the chances of getting cancer. Intermittent fasting is when you switch between eating and not eating, focusing more on when you eat than what you eat. Some popular ways to do this include the 16/8 method, where you eat only during an eight-hour window and fast the other 16 hours, and the 5:2 diet, where you eat normally five days a week but eat very few calories on two other days. In Australia, poor diets cause about 7% of all diseases, contributing to problems like heart disease, stroke, type 2 diabetes, and certain cancers. Globally, diet issues are linked to 22% of deaths among adults over 25.
Recently, intermittent fasting has been talked about a lot because of its possible health benefits. Fasting impacts our metabolism, changing how our bodies use food and energy, which affects how we absorb nutrients and burn sugars and fats. A new study published in Nature found that when mice broke their fast and started eating, their gut stem cells became super active, which helped repair the intestines. These cells seemed to repair tissue better than in mice that kept fasting or stayed on a regular diet. This finding hints that eating after fasting could help the body fix itself, but there might be a downside. Because these cells are so active, it could raise the chances of mutations, which can lead to cancer.
The stem cell boost after eating is driven by polyamines—tiny molecules that help with cell growth. Polyamines are made naturally in our bodies, can come from food, or be produced by the bacteria in our guts. So, this fasting-eating pattern might improve how well cells repair and grow, but it might also increase cancer risk if done a lot. Even though this pattern has been seen in mice, we don’t fully understand the connection between fasting and cancer risk in humans, so more research is needed.
In animal studies, intermittent fasting helped with weight loss, better blood pressure, lower blood sugar, and lower diabetes and heart disease risks. In humans, fasting has been shown to reduce weight, improve metabolic health, lower inflammation, and boost cell repair to remove potentially cancerous cells. But some studies argue that the benefits of intermittent fasting are similar to just eating fewer calories, leaving questions about its real impact on cancer risk in humans.
For cancer patients, fasting has been shown to lessen the bad side effects of chemotherapy and help make treatments work better without hurting healthy cells. Extended fasting might even slow down tumor growth in some patients. Still, some experts urge caution. Mouse studies show that fasting can weaken the immune system, which could make it harder for the body to fight infections, especially in those already sick. However, so far, no studies link fasting to a higher risk of infections in humans.
While people are excited about the possible benefits of intermittent fasting, more research is needed to know its full effects. Short-term benefits like weight loss and general health improvements are well-known, but the long-term effects—especially around cancer and immunity—are still unclear. There are lots of ways to try intermittent fasting, and it doesn’t work the same for everyone, so it’s hard to give advice that applies to everyone. Also, since most people in studies were overweight or had other health problems, the results may not apply to everyone else.