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© 2023 by Kathy Shattler

*These statements have not been evaluated by the Food & Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease. This applies to all pages in this website. None of the information printed herein is meant to replace your personal physician's instructions or advice and referrals from your physician for Medical Nutritional Counseling is requested, but not mandatory.

A Clinical Review of the Fasting Mimicking Diet

Updated: Dec 17, 2019

By Kathryn J. Shattler, BS, MS, RDN

Focus Objective: Review of Prolon, a 5-day fasting mimicking diet (FMD) that replicates the positive metabolic effects seen in fasting by promoting multisystem regeneration, enhanced cognitive performance, the promotion of fat loss and improved healthspan with minimization of the side-effects traditionally associated with fasting such as low blood sugar, fatigue, loss of muscle mass and weight regain.


Fasting, the practice of abstinence from any food or drink except for water, has been practiced for both spiritual and health reasons for a millennium. The practice has its roots in spirituality with the Muslims fasting during Ramadan and Christians, Jews, Buddhists and the Hindus fasting on designated calendar months or days of the year. We will not deal with the spiritual benefits of fasting here, but rather focus on the perceived and evidence-based positive health outcomes associated with fasting and its various forms.

While much of our research on fasting comes from animal models, focus here will be on human clinical trials and subject areas of interest are:

· Changes in weight

· Changes in metabolic parameters associated with type 2 diabetes

· Effects on risk for and progression of cardiovascular disease

· Effects on cancer prevention and progression

We know clinically that the process of fasting results in ketosis and major changes in metabolic pathways, stress resistance, lipolysis, autophagy and cancer response. Medical applications to date include the treatment of epilepsy, rheumatoid arthritis, weight reduction, longevity and increased healthspan. (1)

Types of fasting models

Fasting models can be broken down into intermittent, modified fasting regimens and time-restricted feeding. Alternate day fasting is what the name implies, days of no food intake are cycled with days of normal food intake. Data from these regimens are limited but do show positive reductions in blood glucose, improvement in inflammatory markers and mild weight loss of about 2.5%.

Modified fasting regimens typically provide 20-25% of energy needs on scheduled fasting days. This routine showed positive reductions in visceral fat, the appetite hormone leptin and increases in the weight friendly hormone adiponectin. Significant weight loss was observed along with reductions in fasting insulin but not glucose. There were mixed results with regards to lipid reductions.

Time restricted fasting is based on balancing energy intake with the circadian rhythm. In both animal and human studies, the incorporation of regular fasting intervals and eating in accordance with normal daily circadian rhythms may be important for maintaining optimal metabolic function in a variety of areas. There is a robust area of research in shift workers that show a disruption in the circadian rhythm is associated with an increased risk of obesity, diabetes, cardiovascular disease and cancer. In addition, data from other studies also support the hypothesis that consuming most of the day’s energy needs earlier in the day is associated with lower weight and improved health (1).

Intermittent fasting involves fasting so many days and then following a normal healthy diet for a period of time and then repeating the fasting cycle followed by a pattern of normal healthy eating. Most of our animal and human research is based on this model of fasting.

Problems with water only fasts

When presented with various fasting options the question is frequently asked, “Why not just do a water fast since it doesn’t cost anything and its easy?” The fact is, a water only fast is not that easy, requires discipline and comes with some potential side effects such as:

· Fatigue

· Electrolyte imbalance

· Low blood glucose leading to hypoglycemia

· Loss of lean body mass or muscle

· Maintenance of weight loss difficult

· Extreme hunger

· Dizziness

Depending on the length and repetitions of the fast, nutritional malnutrition may come into play compromising the major goal of health improvement.

What is ProLon?

ProLon is a periodic fasting program of 5 days of a scientific and patented, calorie-controlled diet followed by 3 weeks of normal healthy eating and then repeating the cycle two more times to achieve desired outcomes. The fasting mimicking diet controls for many of the downfalls of a water only fast by providing a limited number of calories in an optimal nutrient base to support the metabolic functions that occur during a water fast but avoids the pitfalls associated with a zero-calorie intake. (2)

What is in Prolon?

ProLon contains 66 totally unique ingredients studied at the University of Southern California under the sponsorship of a National Institute of Health grant. It is a prestigious and successful attempt to realistically mitigate the fasting process while providing an optimal diet.

The diet contains a variety of soups, bars, supplements, drinks, teas and crackers. Day 1 is 1100 calories while each of the other 4 days are about 770 calories. It is gluten and dairy free.

How does ProLon work?

The food kit, studied for 25 years at the University of Southern California, is designed to trigger the body’s identification of the presence of food through the following nutrient sensing pathways:

· IGF-1, MTOR (Mechanistic Target of Rapamycin) and PKA (Protein Kinase A) are 2 key nutrient sensing pathways that recognize the presence of protein, carbohydrates (sugars)

· These nutrient sensing pathways are pro-growth and pro-aging and lead to many common health problems including heart disease and cancer

· ProLon downregulates these pathways enhancing a fasting mode and activating cellular regeneration and rejuvenation (3)

ProLon allows you to eat while tricking your body into acting like its on a fast

What is ProLon for?

ProLon affects many regenerative and rejuvenative changes including effects on a wide range of markers that contribute to aging and ill health. In clinical trials, ProLon has been found to: (3)

Maintain Healthy Levels of:

· Fasting blood glucose

· Cholesterol

· Blood pressure

· Triglycerides

· C-reactive protein

· Stem cells

· Insulin like growth factor (IGF-1)

Improve the following:

· Regenerative Weight Loss driven by visceral fat loss

· Maintenance of lean body mass

· Energy levels

· Skin appearance

Future Directions

With the success of ProLon, the company plans on implementing fasting regimens tailored for a variety of medical conditions including cancer support, multiple sclerosis, Alzheimers support and diabetes control therapy. ProLon is prescribed by 5,000 clinics nationwide.

#fastingmimickingdiet, #fastingmicmicking, #intermittentfasting, #antiaging, #stemcells


1. Patterson RE, Laughlin GA, Sears DD, Intermittent fasting and human metabolic health. 2015. J Acad Nutr Dietetics; 115(8):1203-1212.

2. Brandhorst S, A periodic diet that mimics fasting promotes multi-system regeneration, enhanced cognitive performance, and healthspan. 2015. Cell Metabolism; 72(1):86-99.

3. Brandhorst S., Wei M, FMDs and risk factors for aging, diabetes, cancer and cardiovascular disease. 2017. J. of Sci Translational Med;24(9):377.

FMD Subject results (2)

Water, no matter what type of fast, is important

Kathy J. Shattler

Registered Dietitian Nutritionist