Dietitians have long debated the benefits of diets for sustainable weight loss. Fads come and go, and many don’t live up to their promises. But what happens when we shift our viewpoint on dieting – seeking not to shed pounds but to increase longevity?

That’s what researcher Dr. Valter Longo, the director of the Longevity Institute at the University of Southern California, set out to do when he created the ProLon Fasting Mimicking Diet.

The ProLon diet is a short-term, fasting-mimicking diet, or FMD, intended to boost cellular rejuvenation and increase life length. Melanie Murphy Richter, a registered dietitian nutritionist based in the Los Angeles area and instructor of Nutrition Physiology at the University of California Irvine who previously studied under Dr. Longo, says that weight loss is just "a happy side effect for many people."

Dr. Longo has been studying the impact of calorie restriction and fasting on longevity since the 1990s. He marketed the ProLon diet, which stands for Pro-Longevity, in 2016 as a way for people to benefit from fasting without completely starving themselves.

Research suggests the diet can be beneficial for some users, but harmful to others. Here’s what to know about ProLon.

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What Is the ProLon diet?

The ProLon diet is a five-day, plant-based fasting mimicking diet.

Fasting works against the body’s natural tendency to use food and calories for energy. In a true water-only fast, people do not consume any calories for one to three days, forcing the body to eat away at internal components like fats, proteins and cells for energy instead. This can trigger a process called autophagy, where the body cleans out old cells to make way for new ones.

Researchers have different takes on how long people can safely undergo a water fast, with some suggesting a limit of one to three days and others saying more than a week. Still, it's important to remember that safe does not always equate to healthy. And because everyone has different energy needs, it is important to consult a medical professional before undergoing a fast.

When following an FMD like ProLon, people do consume calories, but at a threshold lower than what the body needs for energy use. As a result, the body continues to act as if it is fasting, and breaking down what’s left of those fats, proteins and cells for energy.

According to ProLon’s website, the diet nourishes the body but does not trigger the cellular food sensors known as nutrient-sensing pathways. This suggests the food is enough to keep the body safe but not to activate processes like digestion, or the body using food as fuel.

What Do You Eat On the ProLon Diet?

People who sign up for the ProLon diet pay $190 (as of September 2023) for a five-day meal kit. Discounts are offered if you order a three-month supply (three five-day meal kits). Foods are packaged in labeled boxes, so that customers know exactly what to eat each day of the five-day fast.

A ProLon meal kit consists of:

  • Olives.
  • Kale chips.
  • Dehydrated soup powders (to mix with hot water).
  • Herbal teas.
  • Nut bars.
  • Vitamin and mineral supplements, including an omega-3 supplement.
  • A proprietary glycerol mix (to mix with water), which the company says fuels and protects muscles.

The meal kit may appear comical to some – including Jordan Hill, a registered dietitian nutritionist and certified specialist in sports dietetics with Top Nutrition Coaching. Hill says reading the ingredient list made her chuckle.

“Those are absolutely things that folks can get from the grocery store and probably spend far less than what they would be spending on these boxes,” Hill says. “But the convenience of something like this is that people don't have to think about it. They don't have to grocery shop; they have a very structured plan for five days.”

ProLon says all ingredients were tested and “carefully selected to work together to keep your body nourished” for the duration of the diet. Meals plans are plant-based and matched with a “specific ratio, amount and composition of plant-derived protein, healthy fats and complex carbohydrates.” According to ProLon, the olives are sourced from the south of Spain, where the food has been associated with longevity.

After the five days are up, dieters are instructed not to return to their typical eating habits right away. Instead, the company suggests dieters undergo a transition day on day 6, eating liquid foods like soups and juices, and later light meals with foods like rice, meat, fish or legumes. They say this is to promote a gradual readjustment to a larger meal plan and to reduce the risk of a binge.

Nutritional Quality of the ProLon Diet

The foods in the five-day kit are formulated to provide a specific balance of each macronutrient (carbohydrates, proteins and fats), as well as the essential micronutrients (vitamins and minerals). Although the total caloric intake is low – each day's worth of food adds up to between 750 and 1,100 calories – the diet claims to meet essential needs. However, this is less than the average recommended daily intake for a toddler, at 1,200 calories.

Richter says that “the foods included in the ProLon fasts are nutrient-dense, meaning they provide essential vitamins, minerals and other micronutrients despite the reduced caloric intake.”

Still, depending on how you look at it, Prolon isn’t so much a diet as it is a form of supplemented starvation. Nutritional value aside, the main purpose of the selected ingredients appears to be that they are low-calorie components of a rigid meal plan. Take it from the company: “In a nutshell, the program allows users to eat while their cells remain in a fasting state.”

Fasting isn't risk-averse, and ProLon alerts users of side effects like dizziness or hunger. The company suggests users talk to a doctor if their hunger gets severe.

The diet could also cause temporary constipation, or give someone the “illusion” that they are constipated because they don't need to use the bathroom as frequently. This can be a typical response from consuming a low volume of food. Fasting and fasting-mimicking diets can also cause the body to temporarily stop using its digestive pathways until it gets more food, Richter says.

Benefits of Fasting

The ProLon Diet is derived from the idea that there are benefits to fasting – once in a while – as this process can clean out toxins and allow for cellular rejuvenation, which is the production of new cells.

In short: Without food available for energy, the body looks for other sources, starting with itself. It begins with eating fat cells, then gets into protein and muscle cells. Since muscle loss isn't a goal for many people, “on face value, that doesn't sound great,” Hill says.

“If we're in this calorie deficit for an extended period of time, we're losing muscle, which is where our strength is,” Hill adds.

Still, some positives of this process are that the body begins eating unessential (or least essential) cells – promoting a clean-up. This can result in fat loss, which is a goal for some people.

Fasting also forces the body into a protective state. When the body senses it's not being fed, it reduces energy expenditure and shuts down certain cellular functions to prioritize essential life functions. Studies, including a 2023 study co-authored by Longo, have demonstrated that fasting may benefit cancer patients undergoing chemotherapy. The researchers showed that fasting forced the body into a protective state which helped it guard healthy cells from the chemo, better streamlining the treatment to target cancer cells.

Risks of Fasting

While short-term fasting can have benefits for the cells, fasting isn’t healthy for everyone and isn’t sustainable long term.

Among other unwanted outcomes, cellular shutdown from extreme fasting or starvation can cause people who menstruate to stop menstruating, or lose their period. Studies say that dieting may halt certain hormone and steroid-making processes, like the making of estrogen or gonadal steroids, which can interfere with menstruation.This can harm the body as the menstrual cycle is an important support for healthy hormones and bone mineral density.

Further, fasting for too long can lead to negative health consequences like starvation, emaciation, loss of muscle mass, cognitive function and death. Even a short-term fast can be detrimental for people who are underweight, at low body mass, or who are at risk for disordered eating (which can be anyone).

Richter says that several groups of people should not undergo this diet due to its risks. Some risk groups include:

  • People who are pregnant or breastfeeding. 
  • People who are under 18 BMI.
  • People living with certain medical conditions.
  • People at risk for or with a history of an eating disorder.

People who are curious about the diet should talk with a medical professional before starting ProLon or any kind of fast, especially if you have any underlying medical condition or diagnosis. It’s better to have open conversations about risks and benefits than to try something in secret without support, Hill says.

“Consult with a doctor, a dietitian and, a lot of times your providers will meet you where you are,” Hill says. “With the support of your health care provider, you can decide whether or not it's right for you.”

Copyright 2023 U.S. News & World Report

2023-08-10T18:55:52Z dg43tfdfdgfd