Updated: July 5th, 2026
- Summer brings great food, fun drinks, and often, frustration with our bodies.
- Fasting is an effective weight loss strategy, but many women have difficulty with it’s rigidity.
- A fasting mimicking diet (FMD) is a great compromise; it “tricks” your body into thinking it’s fasting, so you get the benefits but still get to eat.
- The ProLon Meal Program is a ready-made way to do the five day program, but the cost can be prohibitive.
- You can create your own FMD with the right knowledge and preparation
“It’s been so hot – all I want to do is float in the lake. But I’m so self-conscious about my body that it’s tough to relax,” Barb told me last week. She’s certainly not alone in that; so many of my clients tell me they feel the same way.
With summer in full swing, they’re trying to squeeze into their bikinis – but a long winter filled with comfort foods means their bodies have changed since last summer! And even those who don’t have bikini goals are telling me they aren’t feeling great about their current weight and, more importantly, about the way their bodies feel.
Barb is a great example. A 40-something mother of two, she says she’s not “technically” overweight, but she is a good 15 or 20 pounds over what she envisions as her ideal weight. She’d done some research into the science behind fasting and came to my office excited to try it. She was also armed with both skepticism and a great deal of curiosity. Her biggest worry was that she didn’t have the willpower to stick with a fasting program since she loved food so much – and there are so many events filled with amazing food in the summer months.
I suggested she try what I recommend to many clients who feel like they simply can’t go without eating for as long as a traditional fasting program suggests: a fasting mimicking diet.
Have you heard of this? Many of my clients have, and are quite curious about how a fasting mimicking diet (FMD) can help.
What is a Fasting Mimicking Diet anyway?
Fasting is one of the most ancient healing traditions in human history. It has been practiced by virtually every culture and religion on earth. Fasting and intermittent fasting have become quite a trend in the health world, because they’re being used not only for weight loss, but to improve concentration, prevent insulin resistance and even reverse the entire aging process. But if the idea of not eating for 12, 14 or 16 hours – or even full days at a time – has you seeing stars, you might want to consider the fasting mimicking diet instead.
The FMD provides all the benefits of a fasting diet, but you still get to eat. During the day, food is allowed, but you restrict your calorie intake significantly.
This effectively “tricks” your body into thinking you’re fasting, while you’re actually eating some food over a five-day period, a time-span that’s been associated with the benefits of fasting. The FMD also focuses more on what you can and can’t eat, as well as when you’ll restrict the number of calories you consume.
How Does the Fasting Mimicking Diet Work?
The Fasting Mimicking Diet reduces calorie intake for five days; it’s never about not eating anything at all. The idea is to supply your body with just enough calories to feel satiated, but not full. It’s also designed to allow your body to enter gluconeogenesis, the process by which the body converts fat and other non-carbohydrates to glucose (i.e. body and mind fuel).
For example, on day one, you would consume about 1,100 calories, though this varies depending on your gender, activity levels, and weight. Of those calories, 11% should come from protein, 46% from fat and 43% from carbohydrates. On days 2 through 5, you’ll consume just 725 calories per day, with a macronutrient breakdown of 9% protein, 44% fat and 47% carbohydrate. Hydration is critical throughout the five day period. Aim to drink two to three liters of water a day.
The FMD only requires you to follow the program for five days each month. During the rest of the month, you will rely on regular eating patterns and healthy meals with fresh ingredients. That means that by day six you can slowly transition into light meals – but don’t reach for that burrito or double latte!
During the five day period of restricted eating, it is important to take it easy and go walking, do some stretching, and light yoga rather than vigorous exercise. The idea is to help your body reset.
What are the origins of the FMD?
This approach to eating was pioneered by Dr. Valter Longo, PhD, a highly intelligent and funny Italian biogerontologist, cell biologist and director at the University of Southern California’s Longevity Institute in Los Angeles. Longo is one of the leading researchers on fasting and how it may influence health and longevity.
Based on the impressive findings of his years of extensive research in both animals and humans, Longo founded the L-Nutra technology company and developed the ProLon Fasting Mimicking Diet, a patented meal program you can buy. This helps consumers get on the fasting mimicking program easily and with convenience. The ProLon prepackaged meal kit consists of plant-based, whole foods and does not include the use of any meat or dairy foods, gluten, GMOs or processed foods.
I can see why ProLon is hugely popular among busy New Yorkers and has developed an almost cult-like following among celebrities like Gwyneth Paltrow. The packaging is sleek and modern, and the instructions are straightforward. The meal program includes all the foods you need in measured quantities to stick with the plan for five days.
You get five boxes with all the food you should consume for each day. The boxes include healthy nut bars, kale crackers, olives, soup packets, herbal teas, supplements and the glycerol-spiked hibiscus tea you continuously sip all day. You don’t really have to think about it at all. Following the program takes minimal effort, especially if you don’t mind boxed foods, like dehydrated soup blends, where you just add hot water, and packaged bars. It does come at a bit of a hefty cost, though, at over $200 for the meal kit.
Can you do the Fasting Mimicking Diet without buying a Prolon meal program?
Yes! Of course! If you have the time to get into the kitchen and make all the food yourself then you don’t need to spend that money. You can do a 5 day FMD with fresh, high-quality food for a lot cheaper.
It will require some preparation and cooking, which means you’ll be investing your time instead of money. It’s certainly not impossible and you might actually enjoy the process! You’ll have to pay close attention, as the program requires very strict and diligent adhering to calorie, macronutrient and micronutrient amounts. Many people have done a DIY fasting mimicking diet on their own and there are tons of recipes online that you can follow.
The FMD must meet the following criteria:
- All plant-based
- About 500 calories from complex carbohydrates (vegetables such as broccoli, tomatoes, carrots, mushrooms, etc.) on day 1 of the diet, 400 calories on days 2–5.
- About 500 calories from healthy fats (nuts, avocado, olives, olive oil) on day 1 of the diet; 400 calories on days 2–5.
- About 1100 calories on day 1 of the diet; 800 calories on days 2–5.
- About 25 g of plant-based protein (mostly from nuts) on day 1 of the diet. Less than 18g of plant-based protein on days 2–5.
- Less than 30g of sugar on day 1; less than 20 grams on days 2–5.
- Include a multivitamin/multimineral supplement and an omega 3/6 supplement
What are the benefits of an FMD?
Weight loss is often the immediate goal, but there are many other benefits to following a fasting mimicking diet. More than a decade of research has shown outcomes that are quite impressive.
This method of “fasting with food” also reduces some of the risks tied to extreme fasting, which may include very low blood sugar and/or blood pressure, fatigue, and low productivity. It is a very specific combination of limited plant protein, calorie restriction, good fats, and low-glycemic index carbohydrates that regulates the body’s nutrient-sensing pathways, meaning cells believe they’re not being fed.
At the same time, the diet triggers anti-aging pathways responsible for cellular repair and regeneration for healthy aging. It also activates autophagy – the process of removing damaged and worn-out cellular components, promoting cellular renewal and helping your body rejuvenate. By providing your body with essential nutrients while it’s operating in fasting mode, after multiple (3) consecutive monthly cycles you’re able to maintain lean body mass- something normally lost during a traditional prolonged fast.
But will I lose weight?
Yes, you can definitely lose weight but as with any program, everyone’s results will vary.
And it’s not just weight loss: people lose inches from their waist as well. In a study of 100 people who followed the fasting mimicking diet, each person lost an average of 5 pounds and the majority of this weight loss came from abdominal fat. They also lost 1 inch off of their waist on average.
Of course, if you revert to unhealthy habits like eating everything in sight at that summer barbecue, that weight will come right back. Making healthy choices most of the time is vital to maintaining weight loss!
Who should NOT do an FMD?
Because the program is intense, and seriously limits food intake, there are some categories of people who shouldn’t try it. These include pregnant or nursing women; people under the age of 18; people who are underweight or have a history of an eating disorder.
It’s also not recommended for people who have protein or nutrient deficiencies; have specific dietary needs that are mismatched with the FMD meal plan; are sensitive or allergic to soy, nuts, seeds, or oats (when using the prepackaged foods); and anyone with a chronic medical condition (unless cleared by a medical professional) – particularly blood pressure issues, diabetes, cardiovascular disease, and certain forms of cancer.
The overall takeaway…
Regardless of whether you’re fit and healthy, or have pre-existing medical conditions, you should get the guidance from a registered dietitian or other health professional before starting a fasting mimicking diet. Their guidance will ensure that you’re still getting all the nutrients and vitamins you need for complete nutrition.
Diets are only effective if they are reasonable to follow and maintain. That’s why I often recommend my Drop20 program, which combines natural appetite support, genetic insight, and guided lifestyle strategies. But if you just need a short-term boost, or you’re trying to create healthier habits without doing a full program, the FMD can help.
If you decide to try an FMD, consider your “why”. What do you hope to get out of the experience? People tell me that one lasting benefit isn’t about the five days as much as it was the value of a reset. The FMD allowed them to continue eating mostly clean after they were finished, which helped long term. Many clients tell me they feel so much healthier than they used to on day one. Who wouldn’t want that?
Right after our conversation, Barb decided to give a five day fasting mimicking diet a try. She lost almost four pounds in those five days and feels great! Her biggest takeaway, she said, was how conscious she is now about everything she puts in her mouth.
Though her FMD ended just a couple of days ago, she feels ready to continue eating much smaller portions than she used to, most of them plant based, and limit her protein intake better.
For the first time in years, she said, she really feels like she is on the path to losing the pregnancy weight she never got rid of after having her children. The FMD really worked for her! She feels ready to get that bikini out and enjoy the lake. It’s not too late for you to feel the same this summer!
