Here's What To Know About the ProLon Diet

This "fasting with food" plan is gluten-free and uses mostly plant-based ingredients. Here's what it's all about.

From the keto diet to the Mediterranean diet and dozens of others, it seems like the number of weight-loss diet plans you can follow never ends. Fasting can be appealing as a weight-loss strategy, but it also usually means going without food entirely. If you prefer "fasting with food," the ProLon method, a five-day meal program, might be compelling enough for you to try.

The ProLon method is a fasting-mimicking diet. In other words, the plan shifts your body into fasting mode while allowing you to eat a limited amount of food. When you are fasting, metabolic pathways in your body change to create energy from sources other than food. In the first 24 hours of fasting, your body will break down the glycogen stored in your liver. Once that is gone, your energy will come from fat and stored protein.

Here's a primer on what the ProLon diet is, its benefits, cost, potential downsides, and more.

What Is the ProLon Plan?

The ProLon plan is a fasting-mimicking diet. For five days, you are only allowed to eat proprietary, prepackaged meals.

What is intriguing about ProLon is that it's based on years of research from one of the most well-known longevity experts in the country, and the studies on its outcomes are impressive. It's also in line with some eating philosophies: ProLon is 100% plant-based, gluten-free, and non-GMO, with no artificial additives.

ProLon was created by Valter Longo, PhD, director of the Longevity Institute at the University of Southern California in Los Angeles. The company's research partners include well-respected organizations, such as the Mayo Clinic and the Texas-based MD Anderson Cancer Center.

After over a decade of studies in animals and humans, Longo developed a patented eating plan that activates the body's fasting mode but provides enough food to nourish cells and support metabolic balance simultaneously.

The company says the ProLon diet is designed to regulate the body's nutrient-sensing pathways, which keeps the cells in the fasting state. Fasting diets trigger a process called autophagy, which is associated with longer lifespans.

ProLon vs. Other Types of Fasting

ProLon is considered a type of periodic fasting, as opposed to time-restricted feeding (for example, narrowing your eating window to four-to-eight hours a day) and intermittent fasting (such as eating just 500–600 calories two nonconsecutive days a week).

One study from 2019 compared a control group with no diet intervention to a group that followed ProLon five days a month for three months. The people in the ProLon group lost body weight and belly fat while maintaining lean muscle mass. They also experienced reductions in blood pressure, cholesterol, and CRP (an inflammatory marker); an increase in stem cell production; and a reduction in levels of insulin-like growth factor (IGF-1), a hormone linked to cancer risk when elevated.

In addition, most of the ProLon results were sustained three months after the study was completed. For example, the health benefits of weight lost and reductions in waist measurements were maintained.

What's Included in the ProLon Plan?

ProLon's packaging includes a sleek, modern, glossy white kit reminiscent of unboxing a new MacBook or iPhone. Inside sit five smaller boxes marked Day 1, Day 2, etc. Each contains the food allowed for that specific day, consisting of 73 carefully chosen plant ingredients.

The protocol does not allow you to change the order of the days or swap foods from one day's allotment to another. You can, however, decide how you'd like to arrange your daily meals, although a suggested menu card is provided.

Foods provided include dried soup blends (which require adding hot water), proprietary nut and cocoa-based bars, pouches of olives and kale flax crackers, and a few supplements, including algal oil for plant-based omega-3 fatty acids and a multivitamin/mineral. The kit also contains herbal teas and a large water bottle used to sip a flavored glycerol-based drink, which is used on days two through five to help maintain fullness.

A very straightforward instruction sheet is provided, which lays out how to follow the plan. An FAQ on the brand's website answers additional questions about things like coffee (one cup of black per day is allowed), adding lemon to water (one wedge per day is OK), sprinkling herbs into the soup (one teaspoon per day is permitted), and drinking sparkling water (fine, as long as it's all natural with no artificial sweeteners).

What Following ProLon Is Like

Some people may have an easier time than others getting through the five days. That's because the number of calories a person needs varies depending on factors such as age, sex, weight, height, and level of physical activity. So, a taller person who works a physically demanding job may find following this limited-calorie diet challenging because that person will need more calories than a shorter person who has a more sedentary lifestyle.

Depending on how many calories you normally need, you could find yourself getting hangry on a calorie-restrictive diet. But it's also possible that you could experience a euphoric-like high. There is some evidence showing that fasting has antidepressant-like effects.

One benefit of following this diet is that you will be free from making meal decisions for five days because all of your food is preplanned. However, you may also grow weary of eating only packaged foods, especially if you're used to eating lots of fresh fruits and vegetables.

By day five, you may be ready for ProLon to be over. At the same time, you might also feel a sense of accomplishment for sticking through it for all five days. Once you've made it through day five, the ProLon protocol encourages slowly transitioning back to solid food on day six.

ProLon Results

Results of the ProLon diet are mixed. As the company's website says: Individual results may vary. In other words, some people see the desired results, while others don't. This makes sense, as the research shows that those with the highest BMIs experienced the most significant weight-loss results.

Standard disclaimer:

Standard disclaimer: Body mass index (BMI) is measured by dividing your weight by your height. It has a long history of use in medicine, but is not necessarily a good indicator of health. It does not distinguish between fat and muscle, so someone with very little fat and lots of lean muscle may still be considered overweight or obese by this standard.

Some results, like weight loss and smaller waist size, can be due to water weight and less bloating. After resuming a regular diet, you may maintain some of the waistline difference and weight loss. ProLon provides 1,100 calories on day one and 750 calories on days two through five, which can be very extreme. The impacts may be especially challenging for people who are muscular and have physically demanding lifestyles.

Everyone's experience will be a bit different. And in case you're wondering, you should not extend the program past five days or complete more than one cycle per month. After three months, the company encourages repeating the diet "from time to time" when looking for rejuvenation.

What To Know Before Starting ProLon

ProLon isn't cheap. One kit costs $249, about $50 per day, although this includes a consultation with a registered dietitian or nurse practitioner. If the ProLon diet is in your budget, keep in mind the following tips when you're fasting:

  • Strenuous exercise should not be performed while following the plan. However, light exercise, such as walking, yoga, and stretching, is encouraged.
  • Activities like driving long distances, prolonged sun exposure, or being in a hot tub or sauna should be avoided.
  • The plan also encourages paying attention to how you feel, as side effects like lightheadedness can occur.
  • If you're a person who menstruates, you may want to schedule ProLon in the middle of your cycle (during the luteal phase) because of how water fasting affects female hormones.

There are also several things that may prevent you from starting the ProLon diet:

  • Do not start the diet if you have fever, cough, or diarrhea.
  • Having signs of an active infection or being at risk of recurrent infection are also reasons not to fast.
  • Do not fast if you are pregnant or breastfeeding.
  • Having a history of an eating disorder means this diet is not for you.
  • If any strict eating plan tends to trigger you emotionally, skip ProLon. In other words, if a previous cleanse led to a pizza binge by day two, ProLon is not the plan for you.
  • This diet is also not for people under age 18 years or older than 70 years.

If you have any of the following conditions, do not start a fasting diet without the supervision of a healthcare provider:

As for allergies, all of the ingredients in ProLon food are visible online, so if you have any food allergies or intolerances, you should check to see if you can follow the plan. ProLon states that the diet is inappropriate for those with allergies to nuts or sesame.

A Quick Review

Bottom line: Some people are encouraged to try the diet, while others feel the opposite. The calorie restrictions can be challenging, especially for people who need a higher-calorie diet.

One last piece of advice: don't go it alone. If you don't have a significant other, friend, or family member to do it with you, follow ProLon under the supervision of a registered dietitian who can coach you through the five days. The support and personalized guidance can be invaluable.

ProLon can be an investment in your health. Just be sure to examine if it's the right one for you before you hit the "add to cart" button.

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  1. Sanvictores T, Casale J, Huecker MR. Physiology, Fasting. In: StatPearls. StatPearls Publishing; 2022.

  2. ProLon. What is ProLon?

  3. Min S, Masanovic B, Bu T, et al. The association between regular physical exercise, sleep patterns, fasting, and autophagy for healthy longevity and well-being: A narrative review. Front Psychol. 2021;12:803421. doi:10.3389/fpsyg.2021.803421

  4. Wei M, Brandhorst S, Shelehchi M, et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular diseaseSci Transl Med. 2017;9(377):eaai8700. doi:10.1126/scitranslmed.aai8700

  5. U.S. Department of Agriculture. Dietary Guidelines for Americans 2020–2025.

  6. Wang Y, Wu R. The effect of fasting on human metabolism and psychological health. Dis Markers. 2022;2022:5653739. doi:10.1155/2022/5653739

  7. Zhang Y, Liu C, Zhao Y, Zhang X, Li B, Cui R. The effects of calorie restriction in depression and potential mechanisms. Curr Neuropharmacol. 2015;13(4):536-542. doi:10.2174/1570159X13666150326003852

  8. ProLon. The science behind ProLon.

  9. ProLon. What is the daily caloric intake on ProLon?

  10. ProLon. Should I take ProLon?

  11. ProLon. Can I exercise during and/or after fasting? How should I ease back into my exercise routine?

  12. ProLon. Can I do a ProLon cycle while I'm menstruating?

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