The Fasting Mimicking Diet (FMD) is a periodic nutrition program that involves five consecutive days of calorie restriction, followed by a gradual return to a regular diet.
Unlike traditional diets, it doesn't require ongoing calorie restriction. Instead, it alternates specific periods of reduced calorie intake with periods of regular eating.
One of the most common questions among people following this approach is how much time should pass between cycles: How long should you wait before starting another Fasting Mimicking Diet cycle? Can you follow it every month? How many cycles are recommended throughout the year?
The ideal frequency isn't the same for everyone. It depends on several factors, including body weight, overall health, metabolic markers, and individual goals. Understanding how to space out cycles is essential to following the program appropriately, avoiding cycles that are too close together and periods of inadequate nutrient intake.
How long should you wait between two Fasting Mimicking Diet cycles?
In general, the Fasting Mimicking Diet can be repeated once a month, but not more frequently. It's important to give your body enough time between cycles to return to a complete, balanced diet.
The Prolon program is designed around five consecutive days, during which calorie intake and nutrient composition are specifically formulated to mimic some of the metabolic effects of fasting. Once the fifth day is complete, you gradually return to your regular eating routine.
Monthly cycles have also been used in several clinical studies on the Fasting Mimicking Diet.
However, this doesn't mean you need to complete a cycle every month throughout the year: the total number of cycles should be determined based on your individual health profile.
In particular, recommended frequencies can vary considerably between people looking to support their overall well-being and healthy aging and those with metabolic risk factors who may require closer monitoring.
How many Fasting Mimicking Diet cycles should you do per year?
The number of cycles depends on your individual health profile.
In general, 2–3 cycles per year may be appropriate for people who are in good health or have a low metabolic risk profile.
For those with higher metabolic risk factors, a healthcare professional may recommend a more frequent schedule, potentially up to 12 cycles per year (one per month), depending on individual circumstances and regular health assessments.
How do you know which frequency is right for you?
Determining the most appropriate number of cycles requires looking beyond a single measurement, such as body weight or blood glucose levels.
A comprehensive assessment should take several factors into account:
- Body weight and BMI: Help assess weight status, although they don't provide a complete picture of body composition on their own.
- Waist circumference: Helps assess abdominal fat accumulation.
- Fasting blood glucose and HbA1c: Provide information about glucose metabolism.
- Lipid profile: Includes total cholesterol, HDL, LDL, and triglycerides.
- Blood pressure: Helps assess cardiovascular risk.
- Medical history and current medications: Help identify potential contraindications or circumstances that require additional precautions.
Taken together, these factors help a doctor or qualified healthcare professional determine whether two or three cycles per year may be sufficient or whether a more frequent schedule should be considered.
It's equally important to monitor these markers over time. Improvements in body weight or certain metabolic indicators may lead to a reassessment of the frequency initially recommended.
Why shouldn't you repeat the Fasting Mimicking Diet too frequently?
The Fasting Mimicking Diet is designed to alternate periods of calorie restriction with periods of regular eating. This alternation is a key part of the program.
During the five days of Prolon, your body receives a reduced calorie intake and a specific nutritional formulation designed to mimic some of the effects of fasting without requiring complete food abstinence.
Once the program is complete, it's important to return to a balanced diet that provides adequate amounts of energy, protein, fats, carbohydrates, vitamins, and minerals.
Repeating the program more frequently than recommended means leaving too little time for regular eating between cycles.
Closely spaced or Prolonged periods of calorie restriction may increase the risk of inadequate nutrient intake, loss of lean body mass, fatigue, and other unwanted effects.
For this reason, it's not recommended to complete more than one cycle per month or to combine the FMD with other Prolonged fasts or particularly restrictive eating plans without professional guidance.
The goal isn't to increase the number of cycles, but to find a sustainable frequency that fits your individual needs, while maintaining the balance between calorie restriction and complete nutrition.
What does scientific research say about Fasting Mimicking Diet frequency?
The possibility of repeating the Fasting Mimicking Diet periodically has also been investigated in clinical studies.
One of the most relevant studies in this field was published in 2017 in Science Translational Medicine by Min Wei and colleagues, including Professor Valter Longo.
The study involved 100 generally healthy participants, divided into two groups. One group continued their usual diet, while the other followed a Fasting Mimicking Diet protocol for five consecutive days per month over three months.
After completing the three cycles, researchers observed favorable changes in several markers associated with health and aging, including body weight, total and trunk fat mass, blood pressure, and IGF-1 levels.
A subsequent analysis also found that certain changes in metabolic markers, including BMI, fasting blood glucose, triglycerides, cholesterol, and blood pressure, were more pronounced in participants who already had risk factors at the beginning of the study.
These findings helped support the use of repeated monthly cycles over three months, while also highlighting the importance of considering individual health profiles when evaluating outcomes.
However, the evidence needs to be interpreted carefully. The study evaluated a protocol consisting of three monthly cycles; it doesn't demonstrate that completing 12 cycles per year is more effective or appropriate for everyone. Further research is needed to better understand the long-term effects and determine the optimal frequency for different populations.
What should you do between Prolon cycles?
The time between two cycles shouldn't be seen as simply a break, but as an essential part of the overall process.
After completing the five days of Prolon, it's important to gradually return to regular eating, avoiding particularly large meals during the initial transition.
Day 6 is a transition day, when it's best to choose light, easily digestible foods, before gradually returning to a complete, balanced diet.
During the weeks between cycles, it's important to maintain a few healthy habits:
Follow a balanced diet. Prioritize vegetables, fruit, legumes, whole grains, nuts, and sources of unsaturated fats, while making sure you're getting enough protein and other essential nutrients.
Stay well hydrated. Drinking water regularly throughout the day helps support normal bodily functions.
Stay physically active. Walking, doing aerobic exercise, and incorporating strength training, according to your individual abilities, can help support metabolic health and preserve muscle mass.
Keep track of your health markers. Body weight, waist circumference, blood pressure, and metabolic markers can provide useful information about your progress.
The FMD should be part of an overall healthy lifestyle, not a way to compensate for overeating or achieve quick results through repeated periods of restriction.
Who Should Take Extra Precautions Before Starting Another Cycle?
Not everyone can follow the Fasting Mimicking Diet in the same way.
Before starting a new cycle, it's important to make sure the program is still appropriate for your current health status.
The FMD is not recommended:
- During pregnancy or breastfeeding.
- For individuals under 18.
- For people who are underweight or have a current or previous history of eating disorders.
- For individuals with allergies or intolerances to ingredients in the kit, such as tree nuts or soy.
- For people with type 1 diabetes.
If you have an existing medical condition or take prescription medications, consult your healthcare provider before starting the program.
Even if you've already completed several cycles, you shouldn't decide on your own when to start another one. Regular health assessments help evaluate your individual response and determine whether your cycle frequency should stay the same, be reduced, or be adjusted.
