Fasting is a hot topic in health and wellness, and for good reason.

It’s been associated with a wide range of benefits — from weight loss to boosting your body’s health and life span.

There are many types of fasting methods, such as intermittent fasting and water fasting.

“Fast Mimicking” is a recent fasting trend that restricts calories for a set time period.

This article reviews the Fasting Mimicking Diet, so you can decide whether it’s right for you.

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BOTTOM LINE: The Fasting Mimicking Diet is a high-fat, low-calorie intermittent fasting method that supplies prepackaged meals for five days. It may help you lose weight but is pricey and may not be better than standard intermittent fasting diets.

The Fasting Mimicking Diet was created by Dr. Valter Longo, an Italian biologist and researcher.

He sought to replicate the benefits of fasting while still providing the body with nutrition. His modifications avoid the calorie deprivation associated with other types of fasting.

The Fasting Mimicking Diet — or “fast mimicking” — is a type of intermittent fasting. However, it differs from more traditional types, such as the 16/8 method.

The Fasting Mimicking protocol is based on decades of research, including several clinical studies.

Though anyone can follow the principles of fast mimicking, Dr. Longo sells a five-day weight loss program called the ProLon Fasting Mimicking Diet through L-Nutra, a nutrition technology company that he started (1).

How does it work?

The ProLon Fasting Mimicking Diet plan includes five-day, prepackaged meal kits.

All meals and snacks are whole-food derived and plant based. The meal kits are low in carbs and protein yet high in healthy fats like olives and flax.

During the five-day period, dieters only consume what’s contained within the meal kit.

Day one of the diet provides approximately 1,090 kcal (10% protein, 56% fat, 34% carbs), while days two through five provide only 725 kcal (9% protein, 44% fat, 47% carbs).

The low-calorie, high-fat, low-carb content of the meals causes your body to generate energy from noncarbohydrate sources after glycogen stores are depleted. This process is called gluconeogenesis (2).

According to one study, the diet is designed to provide 34–54% of normal calorie intake (3).

This calorie restriction mimics the body’s physiological response to traditional fasting methods, such as cell regeneration, decreased inflammation, and fat loss.

ProLon recommends that all dieters consult a medical professional — such as a doctor or registered dietitian — before starting the five-day fast.

The ProLon five-day plan is not a one-time cleanse and must be followed every one to six months to obtain optimal results.


The ProLon Fasting Mimicking Diet is a low-calorie, five-day eating program meant to promote weight loss and provide the same benefits as more traditional fasting methods.

The ProLon meal kit is broken down into five individual boxes — one box per day — and includes a chart with recommendations on what foods to eat and the order in which to eat them.

A specific combination of food is provided for breakfast, lunch, dinner, and snacks, depending on the day.

The unique combination of nutrients and reduction in calories is meant to trick your body into thinking it’s fasting, even though it’s being given energy.

Because calories vary between days, it’s important that dieters do not mix foods or carry foods over into the next day.

All foods are vegetarian, as well as gluten- and lactose-free. The purchased kit comes with nutritional facts.

A five-day ProLon Fasting Mimicking Diet kit includes:

  • Nut bars. Meal bars made from macadamia nut butter, honey, flax, almond meal, and coconut.
  • Algal oil. A vegetarian-based supplement that provide dieters with 200 mg of the omega-3 fatty acid DHA.
  • Soup blends. A mix of flavored soups including minestrone, minestrone quinoa, mushroom, and tomato soup.
  • Herbal tea. Spearmint, hibiscus, and lemon-spearmint tea.
  • Dark chocolate crisp bar. A dessert bar made with cocoa powder, almonds, chocolate chips, and flax.
  • Kale crackers. A mix of ingredients including flax seeds, nutritional yeast, kale, herbs, and pumpkin seeds.
  • Olives. Olives are included as a high-fat snack. One pack is provided on day one, while two packs are provided on days two through five.
  • NR-1. A powdered vegetable supplement that delivers a dose of vitamins and minerals that you wouldn’t normally consume during a traditional fast.
  • L-Drink. This glycerol-based energy drink is given on days two through five when your body has started gluconeogenesis (begins to create energy from noncarbohydrate sources, such as fats).

Dieters are encouraged to only consume what is contained within the meal kit and to avoid consuming any other foods or beverages with two exceptions:

  • Soups can be flavored with fresh herbs and lemon juice.
  • Dieters are encouraged to stay hydrated with plain water and decaffeinated teas during the five-day fast.

The ProLon meal kit contains soups, olives, herbal teas, nut bars, nutritional supplements, chocolate bars, and energy drinks. Dieters are encouraged to only eat these items during their five-day fast.

Unlike the majority of diets on the market, the ProLon Fasting Mimicking Diet is supported by research.

Plus, multiple research studies have demonstrated the health benefits of similar fasting methods.

May promote weight loss

A small study led by Dr. Longo compared people who completed three cycles of the ProLon Fasting Mimicking Diet over three months to a control group.

Participants in the fasting group lost an average of 6 pounds (2.7 kg) and experienced greater reductions in belly fat than the control group (4).

Though this study was small and led by the developer of the ProLon Fasting Mimicking Diet, other studies have shown that fasting methods are effective in promoting weight loss.

For example, one 16-week study in obese men found that those who practiced intermittent fasting lost 47% more weight than those who continuously restricted calories (5).

What’s more, very-low-calorie diets have been proven to encourage weight loss (6, 7).

Still, evidence that the ProLon Fasting Mimicking Diet is more effective than other low-calorie diets or fasting methods is currently lacking.

May reduce blood sugar and cholesterol levels

The same small study led by Dr. Longo that linked fast mimicking to fat loss also observed that the Fasting Mimicking Diet group experienced a significant drop in blood sugar and cholesterol levels.

Cholesterol was reduced by 20 mg/dl in those with high cholesterol levels, while blood sugar levels dropped into the normal range in participants who had high blood sugar at the beginning of the study (4).

These results were also demonstrated in animal studies.

Four days of the diet every week for 60 days prompted regeneration of damaged pancreatic cells, promoted healthy insulin production, reduced insulin resistance, and led to more stable levels of blood glucose in mice with diabetes (8).

Although these results are promising, more human studies are needed to determine the diet’s impact on blood sugar.

May reduce inflammation

Studies have shown that intermittent fasting reduces markers of inflammation, such as C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interferon gamma (ifnγ), leptin, interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) (9, 10, 11).

In a study in people practicing alternate-day fasting for the religious holiday of Ramadan, proinflammatory cytokines were significantly lower during the alternate-day fasting period, compared to the weeks before or after (12).

One animal study found that the Fasting Mimicking Diet may be effective at reducing certain inflammatory markers.

Mice with multiple sclerosis were placed on either the Fasting Mimicking Diet or a ketogenic diet for 30 days.

The mice in the fasting group had significantly lower levels of ifnγ and the T helper cells Th1 and Th17 — proinflammatory cells associated with autoimmune disease (13).

May slow aging and mental decline

One of the main reasons Dr. Longo developed the Fasting Mimicking Diet was to slow the aging process and risk of certain diseases by promoting the body’s ability to self-repair through cellular regeneration.

Autophagy is a process in which old, damaged cells are recycled to produce new, healthier ones.

Intermittent fasting has been shown to optimize autophagy, which may protect against mental decline and slow cellular aging.

A study in mice found that short-term food restriction led to a dramatic increase of autophagy in nerve cells (14).

Another study in rats with dementia showed that alternate-day food deprivation for 12 weeks led to greater reductions in oxidative damage to brain tissue and reduced mental deficits compared to a control diet (15).

Other animal studies have demonstrated that fasting increases the generation of nerve cells and enhances brain function (16).

What’s more, intermittent fasting has been shown to decrease insulin-like growth factor (IGF-1) — a hormone that, at high levels, can increase the risk of certain cancer, such as breast cancer (17, 18).

However, more human studies need to be carried out to fully understand how fasting may impact aging and disease risk.


The Fasting Mimicking Diet may promote weight loss, enhance autophagy, and reduce blood sugar, cholesterol, and inflammation.

The biggest downside to the ProLon Fasting Mimicking Diet is cost.

A meal kit currently sells for $249 per box when purchasing up to two boxes — or $225 when purchasing three or more boxes.

Costs can quickly add up if you follow the recommended five-day protocol every one to six months.

What’s more, though there are many human studies on the benefits of intermittent fasting, more research needs to be completed on the ProLon Fasting Mimicking Diet in particular.

It remains unknown whether it’s any more effective than other types of intermittent fasting.

Who should avoid the fasting mimicking diet?

ProLon does not recommend its diet to certain populations, such as pregnant or breastfeeding women and those who are underweight or malnourished.

People who are allergic to nuts, soy, oats, sesame, or celery/celeriac should also avoid the ProLon meal kit as it contains these ingredients.

Additionally, ProLon warns anyone with medical conditions — such as diabetes or kidney disease — to only use the plan under a doctor’s supervision.

Intermittent fasting may also not be appropriate for those with a history of disordered eating.


Pregnant or breastfeeding women, and those with allergies and certain medical conditions should avoid this diet.

The Fasting Mimicking Diet is most likely safe for healthy individuals and may provide several health benefits.

However, it’s unclear whether it’s more effective than other, more researched methods of intermittent fasting, such as the 16/8 method.

The 16/8 method is a type of intermittent fasting that limits eating to eight hours per day, with no food for the remaining 16 hours. This cycle can be repeated once or twice per week or every day, depending on personal preference.

If you have the funds and the self-discipline to follow the five-day, low-calorie fasting plan from ProLon, it may be a good choice.

Just remember that — like other fasting methods — this diet needs to be continued long term to reap the potential benefits.

It’s possible to fast mimic without using the ProLon prepackaged meal kit.

Those with nutrition knowledge can create their own high-fat, low-carb, low-protein, calorie-controlled, five-day meal plan.

Some fast mimicking meal plans are available online but they don’t deliver the same nutrition as the ProLon meal kit — which may be the key to the diet’s effectiveness.

For those interested in trying intermittent fasting, a more researched, cost-effective plan, like the 16/8 method, may be a better choice.


For those interested in intermittent fasting, the 16/8 method may be a more cost-effective choice than ProLon.

The ProLon Fasting Mimicking Diet is a high-fat, low-calorie intermittent fasting diet that may promote fat loss and reduce blood sugar, inflammation, and cholesterol — similar to other fasting methods.

Still, only one human study has been carried out to date, and more research is needed to validate its benefits.