Fasting, drinking only water or juice for a period of time, has long been seen as a way to cleanse the body and promote health. It's not an easy diet path to follow, however. Now a study by researchers at the University of South California Leonard Davis School of Gerontology suggests that a new way of eating they call a Fasting Mimicking Diet (FMD) will not only benefit our general well-being, but actually help us to be biologically younger — by an average of 2.5 years.

Biological age is a measure of the function of our cells and tissues, not our chronological age. As well as extending the overall biological age in humans, the FMD — a diet high in unsaturated fats and low in overall calories, protein and carbohydrates — reduces immune system aging, insulin resistance and liver fat.

The FMD mimics the effects of a water-only fast, but still provides the dieter with necessary nutrients and makes fasting easier to stick to and more appealing.

People on the diet consumed specified amounts of plant-based soups, energy bars and drinks, chip snacks and tea. They were also given a supplement that contained crucial vitamins, minerals and essential fatty acids.

The study was led by Valter Longo, the Edna Jones Professor in Gerontology, Professor in Biological Science and Director of the USC Longevity Institute, who developed the FMD with his team. Their previous research demonstrated various health benefits of a Fasting Mimicking Diet including promoting stem cell regeneration, reducing the side effects of chemotherapy and diminishing signs of dementia in mice.

The men and women in the study were between the ages of 18 and 70 and engaged in a fasting period in which they were permitted to consume specified amounts of plant-based soups, energy bars and drinks, chip snacks and tea. In addition, they were given a supplement that contained crucial vitamins, minerals and essential fatty acids.

They followed the fasting diet for five days. Then they went back to their normal diet for 25 days. All engaged in three to four of these monthly cycles of the Fasting Mimicking Diet.

The results were encouraging. Among people in the study:

  • Blood samples showed reduced diabetes risk factors including lower insulin resistance and decreased average blood sugar levels.
  • Magnetic resonance imaging (MRI) showed a reduction in liver and abdominal fat, which indicates a decreased risk of metabolic syndrome, a group of conditions that raises the chance of developing coronary heart disease, diabetes, stroke and other poor health conditions.
  • Participants' immune profiles were also rejuvenated.

The results make the case that a food-based intervention which doesn't require ongoing dietary or other lifestyle changes can nonetheless make people biologically younger. Longo suggests healthy people between the ages of 20 and 70 consider putting themselves on the fasting diet two or three times a year.

“Although many doctors are already recommending the FMD in the United States and Europe, these findings should encourage many more healthcare professionals to recommend FMD cycles to patients with higher than desired levels of disease risk factors as well as to the general population that may be interested in increased function and younger age,” Longo added.

Don't try fasting or even the Fasting Mimicking Diet without first speaking with your healthcare provider, especially if you're taking certain medications for diabetes or dealing with other medical conditions.

The study is published in Nature Communications.