Side effect of keto-diet in cancer patients

Dietitians say a keto diet could help you lose up to 10% of your body weight. These high-fat, low-carb meal plans trick the body into burning its own fat. They could also help fight a variety of cancers by starving tumors of the glucose they need to grow. On the surface, this seems ideal. But research suggests these diets may have a deadly, unintended side effect for cancer patients.

In mice with pancreatic and colorectal cancer, keto accelerates a lethal wasting disease called cachexia. Patients and mice with cachexia experience loss of appetite, extreme weight loss, fatigue, and immune suppression. The disease has no effective treatment and contributes to about 2 million deaths per year.

“Cachexia results from a wound that doesn’t heal,” the senior author says. “It’s very common in patients with progressive cancer. They become so weak they can no longer handle anti-cancer treatment. Everyday tasks become Herculean labors.”

The authors found pairing keto with common drugs called corticosteroids prevented cachexia in mice with cancer. Their tumors shrank and the mice lived longer.

“Healthy mice also lose weight on keto, but their metabolism adapts and they plateau,” the author explains. “Mice with cancer can’t adapt, because they can’t make enough of a hormone called corticosterone that helps regulate keto’s effects. They don’t stop losing weight.”

Keto causes toxic lipid byproducts to accumulate in and kill cancer cells by a process called ferroptosis. This slows tumor growth but also causes early-onset cachexia. When researchers replaced the depleted hormone with a corticosteroid, keto still shrank tumors but didn’t kickstart cachexia.

“Cancer is a whole-body disease. It reprograms normal biological processes to help it grow,” the lead author says. “Because of this reprogramming, mice can’t use the nutrients from a keto diet, and waste away. But with the steroid, they did much better. They lived longer than with any other treatment we tried.”