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  • Kellie Blake RDN, LD, IFNCP, CMHIMP

A Dietitian Followed the Fasting Mimicking Diet and Here's What Happened

     I followed the L-Nutra Prolon Fasting Mimicking Diet (FMD) for five days and the results were amazing!    To fully appreciate this program, a little background on fasting is necessary.

    Fasting has been practiced in many different ways, by many different cultures, for many different reasons.  The health benefits of fasting have been elucidated through reputable, scientific research.    Fasting and calorie restriction are known to improve cardiometabolic health and increase lifespan (1).  

     Fasting can be practiced in many forms (1):

1. Intermittent Fasting:  No caloric intake for a period of at least 12 hours.

2. Alternate Day Fasting:  No caloric intake one day, no caloric restriction the next.

3. Alternate Day Modified Fasting:  Consumption of less than 25% of caloric requirement alternated with days of no calorie restriction.

4. Time Restricted Feeding:  Calorie consumption is limited to a finite period of the day.

5. Calorie Restriction:  Chronic calorie restriction without malnutrition.

6. Periodic Fasting:  Fasting for 1- 2 days per week and eating without caloric restriction for 5-6 days.

     In all forms of fasting, the benefits lie in the flipping of the metabolic switch(1).  When the metabolic switch is flipped, the body moves from using glucose (by a process called gluconeogenesis) to using fatty acids (derived from fatty acid ketones) (1).  This switch has numerous benefits in terms of brain and cardiometabolic health(1).  For example, insulin sensitivity increases, cardiac risk factors are reduced, abdominal fat is reduced, and mitochondrial function is increased(1).   Fasting also destroys damaged cells and allows the body to rid itself of these cells that can potentially cause disease.

     I was introduced to the Fasting Mimicking Diet (FMD) by the creator, Dr. Valter Longo, PhD.  when I heard him speak at the Integrative Healthcare Symposium in February of 2019. The FMD is a plant based diet developed and tested at the Longevity Institute and DIabetes and Obesity Research Institute of the University of Southern California.  The FMD was sponsored by the National Institute on Aging and the National Institute of Health.  

     Dr. Longo has spent his career researching the science of aging.  With the help of his team at USC, he created a plan to allow the average person to perform a short-term fast that provides all the health benefits of fasting without the negative effects of chronic calorie restriction (hunger, weakened immune system, poor wound healing, extreme low weight, and elevated stress)(2). 

     I have been interested in fasting as a treatment for my autoimmune disease and have practiced intermittent overnight fasting for over a year.  After hearing Dr. Longo speak, I wondered how I would do on the full fasting mimicking diet.  I purchased a copy of his book, "The Longevity Diet" and got to work on learning the science.  

   The FMD is low in protein and sugars, but high in healthy fats.  The research findings by Dr. Longo and his team are unbelievable.  In mice, the FMD increased lifespan, caused weight loss, preserved bone mineral density, reduced tumors by half, cut skin disorders by half, increased stem cell regeneration, and improved cognitive function(2).  Following the success of the mice studies, the FMD was studied in humans.  Again the results were impressive.  After three consecutive cycles of the FMD, abdominal fat decreased, muscle mass increased, fasting blood sugar decreased in prediabetic patients, blood pressure decreased, cholesterol decreased, insulin growth factor 1 decreased (a risk factor for cancer), C-reactive protein decreased (a marker of inflammation), and triglycerides decreased (2).  The FMD goes to the root of the problem and is able to correct underlying dysfunction that leads to disease.  Routine FMD cycles are a reasonable strategy to help prevent disease.

The FMD process:

I ordered directly from the Prolon website, but you can also order through any healthcare provider that is registered with Prolon (disclosure:  I am now a Prolon provider).  My Prolon box arrived in the mail and included my 5 days of meals and snacks and a 32 ounce Prolon drinking bottle to mix the L-drink.  There is also a menu insert to provide recommendations on how to distribute your food each day.

Day 1:  On the first day, you are limited to 1100 calories.   Those calories come from complex carbohydrates and healthy fats.  Water is unlimited and sugarless tea of 3 - 4 cups is allowed.  On day 1 I felt slight hunger as my body was adjusting to the drastic calorie reduction.  The psychological effect of not being able to eat my normal diet was fairly strong.  

Day 2:  This was the most challenging day for me.  The calories provided for the day are reduced to 800.  My hunger wasn't overwhelming, but again I did experience some psychological effects. 

Days 3 and 4:  These days were unbelievable.  Calorie level remains at 800.  I felt like I could conquer the world.  My mind was clearer, I was alert and felt extremely awake.  I had no hunger pangs and I actually purchased my next FMD package on day 3 because I felt so great!  I knew I wanted to repeat the process again.

Day 5:  On day 5, I continued to feel awake and alert, no hunger on the 800 calories.  The psychological aspect returned and I was definitely ready to get back to my usual eating style. 

My results:

*I lost 6 lbs   

*My sleep was more restful 

*Waking up in the morning was easier

*I felt awake and alert throughout the entire day each day

*I had zero pre-menstrual syndrome symptoms (this was a suprising effect - I  normally have bloating, extreme food cravings and headaches - I had none of those effects on the FMD)

*I have less cravings for carbohydrate containing foods

*I am more focused on drinking adequate water daily

*I eat less at meals and feel more satisfied after meals

*I feel a huge sense of accomplishment and am so excited to see the long-term effects

     The most difficult part of this process for me was not being able to exercise strenuously during the 5 day period.  Exercise is a huge part of my life, but taking time off to allow my body to rest was very restorative.  I was able to walk and do yoga.

   I will repeat the FMD twice more to complete 3 cycles in a row, then switch to twice yearly for maintenance.  It's a well designed, well researched, practical, easy to implement plan with so many benefits.  If you're interested in learning more about Dr. Longo's work, visit our Prolon page for more information and a short video presentation.  For optimal results, it is recommended that a plant-based diet be followed between FMD cycles.

     For more information on how functional nutrition can prevent and reverse disease, contact us for a free 15 minute phone consultation.

**The FMD has not been evaluated by the Food and Drug Administration.  The FMD is not intended to treat or cure any disease state.  If you follow the FMD, it is advised that you be monitored by a healthcare professional.


1. Anton, SD; Moehl K; Donahoo W; Marosi K; Lee SA; Mainous AG; Leeuwenburgh C; Mattson, M. (2018).  Flipping the Metabolic Switch: Understanding and Applying Health Benefits of Fasting.  Retrieved from  Obesity (Silver Spring). 2018 Feb; 26(2): 254–268. Published online 2017 Oct 31. 

2. Longo, V (2018). The Longevity Diet.  New York, NY:  Avery.

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