What Is the Fasting Mimicking Diet?

·9 min read

Recently, fasting has become a hot topic in the world of science and nutrition. Studies conducted over the past decade or two have suggested that fasting -- or abstaining from eating food -- for certain periods of time might pay significant health dividends.

It seems counterintuitive that not eating can offer health benefits, but studies have suggested that there could be real benefits to some folks in a variety of health areas, including weight management, modifying the risk of diabetes and reducing the risk of cancer.

The idea behind fasting as a tool for health goes back to our origins as a species. Our ancestors' hunter-gatherer lifestyle -- approximated to some degree with the paleo diet -- produced periods of bounty interspersed with periods of limited caloric intake. The human body evolved to cope with an uncertain food supply, and in fact could thrive during times of food scarcity.

Our modern, largely sedentary lifestyle and 24/7 access to high-calorie foods that are often highly processed and packed with sugar and sodium, however, have derailed the natural processes that evolved over millennia to keep us alive. Research suggests that this constant access to calorie-dense food might be responsible for the explosion in obesity rates we've seen over the past 50 years. Getting back to a more intuitive ebb and flow of calories in the diet theoretically could solve a multitude of health problems.

[Read: Intermittent Fasting: Foods to Eat and Avoid.]

Types of Fasting Diets

But not all fasting is created equal, it turns out, and there's some specifics around how to do it in a way that's supportive to health and won't cause your body to think you're starving and slow down your metabolism to stretch the calories you already have on board.

Lately, there's been a few different approaches to fasting that have garnered a lot of attention, with intermittent fasting and fasting mimicking diets being among the most commonly cited.

Intermittent Fasting

Intermittent fasting can take a number of different forms, with terms such as 16/8 (a daily 16-hour window when you can eat with an 8-hour rest period when you don't consume anything) being a common one. Other approaches to IF include not eating for two or three days per week, not necessarily consecutively. In short, no matter which approach you take, IF dictates when you can and can't eat, but doesn't typically prescribe certain foods.

Cathy Leman, a dietitian, personal trainer, nutrition therapist, speaker, writer and breast cancer survivor based in Chicago, says there's been a lot of excitement around intermittent fasting and the benefits it might offer in terms of curbing obesity and chronic diseases such as cancer. However, she adds, more research is needed to fully understand what's going on with meal timing and how it could improve health.

There's "a lot of evidence from animal studies that intermittent fasting does have favorable effects on insulin metabolism and inflammation, but human studies have not supported those findings yet," she notes.

Currently, the science indicates that "intermittent fasting can be beneficial for some people because it causes them to put their awareness on their eating habits and to be more deliberate when they're eating." For example, if you're prone to late-night snacking, IF can help you correct that habit, which could lead to weight loss and subsequent health benefits.

[READ: The Case for Skipping Meals.]

Fasting Mimicking

Fasting mimicking, on the other hand, usually is more specific about what you can and can't eat in addition to when you'll restrict the number of calories you consume. The idea here is that fasting -- going completely without food for a time -- has some solid scientific evidence backing it. But it can be difficult to completely forego food and even more challenging to fast long enough to derive any real benefits from the practice.

Enter fasting mimicking, which seeks to offer a less challenging way of garnering the benefits of a full fast. The approach effectively "tricks" your body into thinking you're fasting while you're actually still taking in some food over a five-day period, a time-span that's been associated with the benefits of fasting.

The fasting mimicking diet was created as means of finding a sweet spot between too much and too little food. This approach to eating was pioneered by Dr. Valter Longo, a biogerontologist and cell biologist at the University of Southern California who has conducted extensive research into food restriction and how it may influence health and longevity. Based on the findings of his research, Longo founded the L-Nutra technology company and developed the ProLon Fasting Mimicking Diet to help consumers get with the fasting mimicking program.

How Fasting Mimicking Works

"The fasting mimicking diet is a reduced-calorie diet with a specific macro- and micronutrient breakdown that makes your body think it's fasting while still allowing you to consume reduced amounts of food," says Kristine Dilley, a dietitian at the Ohio State University Wexner Medical Center Comprehensive Weight Management Clinic in Columbus.

The diet lasts for five days, and the approach breaks down as follows:

-- On day 1, you consume 1,100 calories. Of those calories, 11% should come from protein, 46% from fat and 43% from carbohydrate.

-- 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.

During each of the five days, you should consume a minimum of 70 ounces of water daily. The five-day fast period should be repeated once per month for a minimum of three months to achieve optimal results, Dilley explains, and you should avoid caffeine during the five-day fasting period.

[Read: Can You Do Keto and Intermittent Fasting Together?]

Pre-Packaged Food Options

Though anyone can follow the principles of a fasting mimicking diet and do it on their own, the ProLon Fasting Mimicking Diet features a meal program you can buy. Dilley says 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." It also contains a supplemental energy drink and a plant-based omega-3 supplement.

The program has undergone clinical trials at USC and has been patented. The meal program includes all the foods you need in measured quantities to stick with the plan for five days.

Cost of the Fasting Food Plan

The company currently offers three plans, ranging from $249 for a single box to $225 per box for three or more boxes or a subscription plan. Users are recommended to follow the plan once per month for anywhere from one to six months.

Compared to other fasting approaches, such as intermittent fasting, which simply alters the timing of food intake rather than the foods themselves, the ProLon program can be more expensive and might increase your spending when you consider that you'll still have other grocery expenses during the month. "Other fasting diets would not alter grocery expenses as they don't require specific food choices but rather limit the times the food is eaten," Dilley says.

Each ProLon plan includes an optional complementary coaching session with a health coach and free shipping. A portion of each sale is donated to the Create Cures Foundation, a nonprofit founded in 2015 by Longo that's dedicated to the purpose of promoting creative, educational and scientific programs aimed at ensuring healthy lives, improving well-being and reducing mortality. The company also offers a customer assistance program to help low-income individuals access its products.

Does Fasting Mimicking Work?

The fasting mimicking diet purports to carry many of the same health benefits of other fasting regimens such as:

-- Weight loss.

-- Reduced belly-fat.

-- Decreased cholesterol levels.

-- Decreased blood sugar levels.

-- Decreased inflammation in the body.

The fasting mimicking diet also claims to slow the aging process through improved cell-repair -- a process called autophagy -- and cellular regeneration, Dilley says. "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."

There are some studies to back up these claims. " One study on humans indicated that three cycles of a five-day fasting mimicking diet per month was effective in reducing body weight, waist circumference and BMI, systolic blood pressure and IGF-1, a marker associated with aging," Dilley explains.

These effects were found to be sustainable for up to three months after completing at least three monthly cycles, she adds. But this frequency can be onerous and expensive, and may not be suitable for all. "You need to assess whether you could comply with a restrictive diet on an ongoing basis and whether the diet is financially feasible."

There could also be some potential downsides to following a fasting mimicking diet, and it's best to check with your doctor before embarking on a plan, whether you purchase a ProLon plan or attempt to do it yourself.

For example, dehydration is one area of concern because you'll be limiting the amount of food you take in, which can be a source of fluid. It's important to follow the recommended fluid intake and be sure you're drinking enough water, Dilley says.

"There's also a risk for possible adverse effects on individuals taking medications that may be affected by food and fluid or specific nutrient intakes."

Who Should Use a Fasting Mimicking Diet?

"The diet is best suited for healthy individuals looking to achieve the potential benefits offered by the diet," Dilley says. And there are certain people who should avoid it, including:

-- Women who are pregnant or breast feeding. Women need to take in more calories, not fewer, when pregnant or breastfeeding because these activities gobble up a lot of energy.

-- People with nutritional deficiencies or those who are underweight. Cutting out so much food can make existing nutritional deficits worse.

-- People with a history of eating disorders. Restricting your food intake can be triggering for people who have or have had an eating disorder and could lead to unhealthy behaviors.

Dilley adds that people with a preexisting medical condition, such as hypertension, diabetes, liver disease or another chronic condition should consult a physician prior to starting this or any other new diet.

Lastly, Dilley notes that "all diets are only effective if they're reasonable for you to follow and maintain. Some patients may benefit from a program that's this structured and takes the guesswork out of planning their diet, while others may not be able to comply with the strict limitations of what's allowed on the diet."

Also, because the fasting mimicking diet allows for unrestricted eating during three weeks of the month, with just the one, five-day fasting mimicking period, that may be easier for some people to stick with. "However, the hefty price tag may be prohibitive for many to be able to stick with the diet long enough to show benefits" or to keep them for the long term.

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