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Fasting diets aren’t just for detoxes or weight loss goals but are now showing the first evidence of creating new cells naturally and protecting the immune system. Researchers from the University of Southern California have stumbled upon clues on how to age healthier and published their findings in the journal Cell Stem Cell, Medical Daily reports.

"When you starve, the system tries to save energy, and one of the things it can do to save energy is to recycle a lot of the immune cells that are not needed, especially those that may be damaged," the study’s coauthor Valter Longo, professor at the USC Davis School of Gerontology and director of the USC Longevity Institute, said in a press release. "What we started noticing in both our human work and animal work is that the white blood cell count goes down with prolonged fasting. Then when you re-feed, the blood cells come back. So we started thinking, well, where does it come from?"

When researchers cut off the food source for both mice and human trials, their white blood cell counts dropped. The cells are responsible for fighting disease and typically flood the body when danger circulates into the blood. However, when they dropped in count something strange happened — the fasting cycle naturally "flipped a regenerative switch" on. "We could not predict that prolonged fasting would have such a remarkable effect in promoting stem cell-based regeneration of the hematopoietic system."

After the test subjects went without food for two to four days over the course of six months, the hematopoietic system killed older and damaged immune cells and generated new ones The system is made up of the organs involved in creating new blood, leading the scientists to believe their findings will have major impacts on healthier aging. "We are investigating the possibility that these effects are applicable to many different systems and organs, not just the immune system," Longo said.

Beyond the basic benefits of fasting

Fasting forces the body to store sugars, fats, and ketones, and to break down a significant amount of white blood cells. Ketones are produced when the body turns fat into energy or fuel, and are a major player in weight loss. Intermittent fasting allows the body to use fat as its primary source of energy, which is why many athletes use it to hit lower body-fat percentages for competitions.

It can help speed up the metabolism and improve bowel movements by giving your digestive system a rest. Periods without food boost the metabolism to burn through calories more efficiently — in a way reminding the body how healthy digestion is done.

Think of fasting as a reset button for the body. It creates a healthy environment for the body to release regulated hormones in order to experience what true hunger feels like. People who eat every three to four hours don’t get to experience the body’s ability to signal true, natural hunger. When the body is temporarily freed from digestion for 12 to 24 hours, it’s also able to focus its regenerative abilities on other systems, such as the skin. Fasting is known to help the body remove toxins and regulate filtering organs such as the liver and kidney. The body shouldn't experience periods of fasting longer than four days, and throughout the entire process water intake should be increased.

With each fast the white blood cell depletion triggered new cells in the immune system. When the enzyme PKA was reduced along with the cells in the fasting process, that’s when Long and his team realized there was a switch being flicked on. The switch made it possible to create new cells and also lowered the levels of IGF-1, a hormone that’s linked to aging, tumor growth, and cancer risk.

"PKA is the key gene that needs to shut down in order for these stem cells to switch into regenerative mode," Longo said. "It gives the 'OK' for stem cells to go ahead and begin proliferating and rebuild the entire system. And the good news is that the body got rid of the parts of the system that might be damaged or old, the inefficient parts, during the fasting. Now, if you start with a system heavily damaged by chemotherapy or aging, fasting cycles can generate, literally, a new immune system."