Fasting Mimicking Diet: What Is It & What Are The Benefits?

I have been using a form of periodic fasting called a fasting mimicking diet (FMD) in my clinic with my patients, which has some pretty great benefits (similar to those from fasting). Here are some general and brain-specific data on the FMD and why you might be interested in trying it, plus how to take part in this eating plan.

The FMD is the evolution of decades of pioneering work on longevity by Valter Longo, M.D., and his team at the University of South California. Longo is recognized as a leading expert on longevity, and has done great work in describing the basic biochemical pathways by which cells age. The FMD program was patented by Longo after years of basic and preliminary research in yeast and animal models.

During the five days of restricted calories, exercise and alcohol are prohibited and coffee is limited to zero or one cup a day. The program is also rich in nuts—so it’s not appropriate for those with a nut allergy—and requires eating whole olives (something to note if you dislike olives).

What is so special about the FMD? The science behind its success.

After years of experimenting with FMD in animal models and showing its benefits on metabolism and life span1, Longo’s team analyzed the effects in a human clinical trial. One hundred healthy subjects participated in this study; half of them followed a Prolon FMD five days a month for three months, and the other half ate their usual diet. Profound differences were seen in terms of weight loss, visceral fat loss, drops in blood pressure, blood sugar, blood cholesterol, and markers of inflammation2 in the FMD group.

There are even provocative data suggesting that combining this FMD with cancer chemotherapy may lead to improved success and fewer side effects3. While much more research is needed before we can make those definite claims, the data we do have sure looks promising.

Overall, these preliminary data are encouraging. It seems the best brains may result from the least calories, at least for five days a month.

After that, Longo has said you can repeat the Prolon FMD monthly as often as you like. For most, a few times a year to capture the benefits is reasonable. I advise my patients that if they want to achieve the published results, they might want to do three cycles chosen at times that they do not have conflicting events, like weddings. Although not studied, a few patients of mine have done it back to back over 10 days, but not at my recommendation. While those patients did fine, it's always best to follow the guidelines on the website and research. 

While the health benefits can be profound, there are some groups of people who should probably not do this eating program (in addition to people who don't like olives). The website for Prolon FMD has clear guidelines on who should not participate in the program, and I endorse those recommendations with my patients. They include:

As always, it's best to consult a doctor before starting any restrictive diet before deciding if it can work for your lifestyle.

Want to learn more from Joel Kahn? Check out the first-ever functional nutrition training, where he teaches classes on heart health and veganism.