Monthly cycles of faux fasting prevent obesity in unhealthy mice
Scientists continue to explore the connection between fasting and the consequences for human health, both good and bad, and part of this research includes diets that merely mimic its effects. A new study has shown how short spurts of these so-called fasting-mimicking diets can bring about a range of benefits in otherwise unhealthy mice, ultimately preventing the buildup of fat and onset of obesity.
Fasting-mimicking diets (FMDs) are low-calorie diets that are designed to trick the body into a fasting state, and we've seen some interesting studies around the various ways they can influence health. A pair of papers from 2017 showed that FMDs in diabetic mouse models could restore insulin production and stabilize blood glucose, as well as regenerate the pancreas. Another from last year showed how FMD diets might improve chemotherapy outcomes in cancer patients.
A team from the University of Southern California set out to explore how FMDs can influence obesity and heart health. To do this, they placed one group of mice on a high-calorie, high-fat diet for two years where 60 percent of their calories came from fat, leading the rodents to become unhealthy and overweight. Meanwhile, a second group were placed on the same diet, but every four weeks were fed an FMD for five days, followed by two days on a normal healthy diet. A third group of mice were fed a consistently healthy diet across the same period.
These experiments showed that the regular five-day cycles of FMD undertaken by the second group of mice counteracted many effects of the otherwise unhealthy diet. This was found to reduce the accumulation of both visceral and subcutaneous fat, while preserving lean body mass. The FMDs also improved cardiovascular function, prevented blood sugar and cholesterol levels from increasing, and positively altered gene expression associated with metabolism. Ultimately, the monthly FMD cycles appeared to prevent obesity in the unhealthy mice, and saw them live as long as the third group fed a healthy diet.
“The study indicates that it’s possible for mice to eat a relatively bad diet that is counterbalanced by five days of a fasting-mimicking diet,” said study senior author Valter Longo. “Our major discovery is that intervening with this diet made their hearts more resilient and better functioning than the mice who only ate a high-fat, high-calorie diet.”
The researchers emphasize that these results should not be taken to mean that an unhealthy lifestyle can be cancelled out by regular period of fasting. They do plan to explore the mechanisms further through clinical trials, however, and imagine further work might lead to a more manageable dietary intervention than those requiring dramatic daily changes, such as the ketogenic diet. It is also unclear how the frequency and timeline used in these mouse experiments would translate to a dietary regime in humans.
“Even after the mice in experimental group went back to their high-fat, high-calorie diet, the improved fat breakdown in their bodies continued for a fairly long period,” Longo explained. “Is there a similar sweet spot for humans, where you can intervene for a few days and still keep breaking down fat for several weeks?"
The research was published in the journal Nature Metabolism.