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Fasting Mimicking Diet: What and How to Eat For Optimal Results

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Kasparas Aleknavičius, MD November 22, 2021

Fasting mimicking diet (FMD) is a 5-day eating plan. You will have to follow the eating plan for five days in a row each month. And for obtaining optimal results it is recommended to be followed every one to six months.

Periodic fasting has demonstrated benefits in extending the lifespan and reducing the risk of many chronic illnesses. For example, diabetes, heart disease, obesity, and disorders of the brain cells. Currently, two methods of fasting are popular among people. They are intermittent fasting (IF) and alternate-day fasting (ADF).

Nonetheless, many people, especially older adults, cannot adhere to longer periods of fasting. Notably, IF requires you to go without food for 12 to 24 hours. Moreover, traditional IF methods are not suitable for people with an eating disorder in the past. FMD apparently overcomes these limitations of IF and gives you similar benefits. While IF is more of an eating pattern than a specific diet, FMD focuses on specific foods to eat five days each month.

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What is a Fasting Mimicking Diet? Learn the Basics

As the name suggests, FMD mimics the physiological state of fasting. Simply put, it tricks your body into believing that you are fasting but you are actually eating selected foods. The brainchild of Professor Valter Longo, the FMD program comprises low-protein, low-carb, and high-fat meals. According to Longo, a fasting mimicking diet promotes health in a way similar to fasting but with meals that contain certain nutrients.

What are the Benefits of Fasting Mimicking Diet?

An increasing body of evidence shows FMD can be effective in the management of obesity. Besides, some studies have found that it can also help improve your gut health and reduce inflammation.

Fasting mimicking diet for weight loss

When you follow the fasting mimicking diet, you consume only small amounts of carbs. Carbs are the primary source of energy for the body. Thus, depriving your body of carbs causes it to use other sources to fulfill its energy requirements. These include glycogen (stored in the liver and muscle) and noncarbohydrate molecules such as glycerol and amino acids. This partially explains how the FMD meal could promote weight loss.

Furthermore, one study suggests that people following the FMD program typically consume 34–54% of their normal calorie requirements. This creates a calorie deficit, which is the key to losing weight.

In a 2017 study, researchers found that by following the FMD program for three months, participants were able to shrink their waist and lose weight. Moreover, they also had healthy blood pressure.

Fasting mimicking diet for gut health

An unhealthy gut can trigger many chronic diseases. Thus, it is critically important to take care of what goes into your gut. Sadly, a typical Western diet contains many ingredients that are harmful to the friendly bacteria in the gut.

A fast mimicking diet can help improve your gut health in two ways:

  • First, it is rich in fibers. These include oligofructoses, fructo-oligosacharides, and galactomannan. Friendly bacteria can use these fibers to feed themselves.
  • Second, it can reduce inflammation in the gut and promote the growth of friendly bacteria. Increased gut inflammation has been linked to many chronic diseases. For example, allergies, joint disease, and heart disease.

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What to Eat and Avoid on A Fasting Mimicking Diet?

The FMD program is a 5-day meal program. On the first day, you consume 1100 to 1150 calories. On the remaining four days, you are not allowed to consume more than 750 to 800 calories per day. The basic idea is to get 60% of your daily calories from healthy fats, 10% from plant-based protein, and 30% from slow digestible carbs on day 1. On the remaining days, the ratio of macros changes slightly to 9% from protein, 44% from fat, and 47% from carbs.

Fasting mimicking diet does not allow the intake of animal protein, processed sugar, lactose, and gluten. Nuts are an essential part of the meal program. Thus, you should take care if you are allergic to nuts. Nut allergy can cause life-threatening reactions in some people.

Food to eat

  • Macadamia nut butter
  • Honey
  • Flax
  • Almond
  • Coconut
  • Algal oil
  • Mushroom and tomato soup
  • Herbal tea, such as spearmint, hibiscus, and lemon-spearmint tea
  • Chocolate bars that contain cocoa powder, almonds, chocolate chips, and flax
  • Kale
  • Herbs
  • Pumpkin seeds
  • Olives
  • Vitamin and mineral supplements
  • Plenty of water
  • Decaffeinated tea

Food to avoid

  • Processed sugars
  • Animal protein
  • Gluten
  • Lactose
  • Coffee (it may be allowed sometimes but you cannot add sugar or cream)
  • Alcohol (no amount of alcohol is allowed)

Below is a breakdown of how to take your foods.

Day 1

Because this is the first day of the program, you may feel a bit lethargic. However, you should start feeling better as your body adapts to a new dietary regimen. Aim for an 1100-calories total intake. Of the total calories, 500 calories should come from complex carbs, 500 calories from plant-based fats, and 100 calories from protein obtained from plant sources.

Day 2, 3, 4, 5

Aim for an 800-calories total intake. Of these, complex carbs should provide 400 calories and healthy fats should provide the remaining 400 calories.

Day 6 and onwards

Avoid eating large meals as they can upset your stomach. Just like day 1, day 6 is the transition from fasting to normal eating habits. To make sure the transition is not painful, start by eating foods that are gentle on your stomach. For example, broths and juices.

You may continue your normal eating habits on other days. However, most experts recommend sticking to plant-based foods and healthy fats for sustained benefits.

Fasting Mimicking Diet for Diabetes: What Does the Science Say?

Fasting mimicking diet has shown promising results in animal studies. According to a 2018 study, diabetic mice that received the FMD for four days every week had:

  • Near-normal blood sugar levels by day 60.
  • Pre-diabetes insulin secretion by day 30.
  • Improved plasma levels of insulin by day 90.

Likewise, researchers have also successfully restored beta-cell function in people with type 1 diabetes, reports ScienceDaily. That said, these results should be interpreted carefully because there is still a dearth of large human studies. If you have diabetes and want to try fasting mimicking diet, always consult your doctor first. Doing so can save you from dangerous changes in blood sugar levels.

Fasting Mimicking Diet Do It Yourself: Can You Do It at Home?

Fasting mimicking diet do it yourself (FMD DIY) may seem like an interesting idea. If you are generally healthy and have no chronic health problems, you may go ahead with FMD DIY. Start with moderate calorie restriction and mostly consume plant-based foods. You may create your eating plan based on the principles of FMD. The principles include eating:

  • Plenty of whole grains, vegetables, and beans. They are the sources of complex carbs.
  • Plant-based protein foods. For example, beans, seeds, and nuts. You may occasionally consume protein from animal sources, fish or seafood.
  • Foods that contain very little saturated fats.

That said, avoid starting the FMD program on your own if you:

  • Have chronic illness
  • Are pregnant or breastfeeding
  • Take medications (prescription or OTC)
  • Are underweight

Key Takeaways

  • Fasting has incredible health benefits. These include healthy weight loss, improved brain function, and lower risk of chronic diseases.
  • Fasting mimicking diet may offer similar benefits. It might be an effective alternative for people who cannot do severe forms of fasting.
  • You may combine FMD with other popular diets such as the IF 12:12, 14:10, 16:8.
  • Most studies have used a 5-day monthly fasting program for three months. Depending on your response and desired outcomes, you may choose to use it for a longer period.
  • Seek professional help to address your specific needs and achieve the desired goals. Only an experienced health professional can assess the risks and benefits and design a plan that best meets your needs.

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Kasparas Aleknavičius, MD
  • Head of Medical Affairs at Kilo Health
  • Medical Doctor at Vilnius University, Lithuania
  • Partnering with the EU-funded Young50 and EUPAP projects

Kasparas Aleknavicius is a medical doctor that graduated from Vilnius University, working as head of medical affairs at Kilo Health. After nearly 5 years in the industry, Kasparas focuses on digital health and is looking for innovative ways to help people lead healthy lifestyles through digital health and wellness platforms.

You can find Kasparas on LinkedIn and follow his latest research on Medium.

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