How Safely Fasting Might Help Support Your Health

Correction: The original headline for this article stated Study Finds that Fasting for 72 Hours Can Regenerate the Entire Immune System. However, a HealthFeedback article recently came to our attention which stated that the study did indeed find that fasting helped to protect against chemotherapy-induced immunosuppression, but this observation was made in mice, not humans.

Everyone wants a long lifespan, but these days many people live a sadly shorter “healthspan.” That’s the term scientists working in the field of aging and longevity research use for the healthy part of your lifespan. While your lifespan might be long, your healthspan can be shorter if you suffer from chronic diseases like diabetes, coronary artery disease, and hypertension.1

Only a few generations back our ancestors rose at daybreak, devoted heavy physical labor to growing/hunting/preparing food, and went to bed after a brief evening lighted by a kerosene lamp or candles. In contrast, our modern days gently transition into late nights thanks to endless artificial illumination and many of us have 24/7 access to a vast array of processed foods. Our bodies have had little more than a century to adjust.

As health researchers grapple with treatments for chronic diseases that accompany a current obesity rate in the U.S. that has tripled in the last 50 years, some have stepped back to learn from rodents about what can be done to enhance the healthspan of humans.2

Timing is Everything

It turns out that many animals (our ancestors included) fast naturally—meals are consumed during daylight. Nighttime is for sleeping. There is a beneficial biological response to this: Both intermittent fasting (IF– often done by only eating during 8 hours each day and fasting for the other 16 hours) and periodic fasting (when caloric intake is restricted for multiple consecutive days) have been shown to result in benefits ranging from disease prevention to enhanced disease treatment.2

After processing our last meal of the day, our digestive systems switch over to what one researcher calls “self-maintenance.”2It is an essential recovery phase. When we eat a last meal late in the evening or snack our way to bedtime, there is less and less of that important time for self-maintenance before we break the overnight fast (breakfast!) with our first meal of the day.

Incredibly, research has found that longer periods of fasting can enable some people with chronic diseases like diabetes to resettheir immune systems, thereby giving renewed length and quality to their healthspan. Initial research done with mice on a water-only 4-day fast by Valter Longo, PhD and his colleagues at the University of Southern California Longevity Institute revealed beneficial biological mechanisms triggered at the cellular level which provided positive lifelong effects.3

A Timewriter shared comments by Dr. Mark Mattson, chief of the Laboratory of Neurosciences at the National Institute on Aging who has written about fasting in cycles of feast and famine from an evolutionary standpoint observing, “natural selection would have favored individuals whose brains and bodies functioned well in a food-deprived state.” Mattson explains that the stress of fasting is beneficial in the same way that the stress of exercise is beneficial, stating “these cycles of challenge, recovery, challenge, recovery seem to optimize both function and durability of most cell sites.”4

Dr. Longo observed that “Strict fasting is hard for people to stick to, and it can also be dangerous, so we developed a complex diet that triggers the same effects in the body.”3The research team called it a fasting-mimicking diet (FMD) and have more recently demonstrated that “brief cycles of periodic fasting-mimicking diets have a range of beneficial effects on aging and on risk factors for cancer, diabetes, heart disease and other age-related diseases in mice and humans. More recent studies have also shown promise for treating multiple sclerosis and Crohn’s disease.”5

Clinical trials in humans following 5 days of FMD each month for three months has shown “reduced body weight and body fat [especially belly fat], lowered blood pressure, and decreased hormone IGF-1 [insulin-like growth factor 1] which has been implicated in aging and disease.”6,7

A fascinating mechanism behind the immune system reset was first seen in mice that experienced the growth of new insulin-producing pancreatic cells. According to Dr. Longo, “Cycling a fasting-mimicking diet and a normal diet essentially reprogrammed non-insulin-producing cells into insulin-producing cells. By activating the regeneration of pancreatic cells, we were able to rescue mice from late-stage type 1 and type 2 diabetes. We also reactivated insulin production in human pancreatic cells from type 1 diabetes patients.”8

FMD Details

Dr. Longo’s fasting-mimicking diet for humans tricks the body into thinking you are fasting while still providing key plant-based nutrients. The research worked with chefs to create a set of 5-day meal kits containing micro- and macro-nutrients that provide optimal nourishment while mimicking the fasting state. The program is the first ever recipient of a U.S. patent for reversal of aging.9The 5-day ProLon plan provides about 750 to 1,100 calories per day. Plant-based nutrients come from whole foods packaged as soups, bars, crackers, olives, drinks, and supplements. A healthy diet is recommended for the remaining 25 days of the month. Research has shown that stem cell-based rejuvenation continues for up to 5 days after the fast and ProLon recommends doing the 5-day fast once a month for three consecutive months.10

Dr. Longo was named by Timeas being among 50 People Transforming Health Care in 2018 for his remarkable work.11He donates all profits from his share of ProLon and 100% of his book royalties to the Create Cures Foundation whose mission is to help fund ways to prevent illness and promote longer, healthier lives.12


It is always a good idea to speak with your health care provider before considering any diet program. There is still more to learn about the effects of fasting, whether intermittent or fasting-mimicking, on health in humans. A Harvard Heart Letterearlier this year shared thoughts from Dr. Frank Hu, chair of Harvard’s school of public health with some potential concerns about intermittent fasting, including that “’there’s a strong biological push to overeat following fasting periods…[and] people who take medications for blood pressure or heart disease also may be more prone to electrolyte abnormalities from fasting.’”13 One journalist who tried the ProLon diet reported, “A diet based on caloric restriction might make you live longer. It’ll certainly feel like longer.”14

Article revised and updated to accurately reflect current research 08/10/2019</

  1. Crimmins EM. Crimmins EM. Lifespan and Healthspan: Past, Present, and Promise. Gerontologist. 2015;55(6):901–911
  2. Longo VD, Panda S. Fasting, Circadian Rhythms, and Time-Restricted Feeding in Healthy Lifespan. Cell Metabolism. 2016;23(6):1048–1059,
  3. University of Southern California. Press Release. Diet That Mimics Fasting Appears to Slow Aging: Benefits Demonstrated in Mice and Yeast; Piloted in Humans. 18 June 2015.,
  4. Heid M. What is Intermittent Fasting and Is It Actually Good for You? Time. 1 August 2018.,
  5. Belman O. Eat Less, Live Longer? The Science of Fasting and Longevity. University of Southern California Leonard Davis School of Gerontology. 18 April 2019,
  6. Wei M et al. Fasting-Mimicking Diet and Markers/Risk Factors for Aging, Diabetes, Cancer, and Cardiovascular Disease. Science Translational Medicine 2017;9(377): eaai8700.,
  7. Cheng C-W et al. Fasting-Mimicking Diet Promotes Ngn3-Driven β-Cell Regeneration to Reverse Diabetes. Cell 2017;168, 775–788,
  8. Newcomb B. Fasting-mimicking Diet Reverses Diabetes in Mice. USC Leonard Davis School of Gerontology News. 23 February 2017,
  9. Kahn J. The First U.S. Patent for The Reversal of Aging: The ProLon Fasting Mimicking Diet. 2 August 2018. Medium,
  10. ProLon. Frequently Asked Questions.,
  11. Oklander M. Health Care 50: 50 People Transforming Health Care in 2018. Valter Longo: The Fasting Evangelist. Time
  12. Create Cures Foundation. Mission,
  13. Harvard Health Letter Not So Fast: Pros and Cons of the Newest Diet Trend.,
  14. Piore, Adam. I Tried Prolon’s Starvation Diet So You Wouldn’t Have To. MIT Technology Review. 20 August 2019.,
  15. Image Source,

via: Healthy Holistic Living

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