Fasting may support weight loss and metabolic health while activating biological pathways associated with healthy aging. Yet going without food for days—or even skipping a few meals—can be challenging for many people.
“I’ve never seen any other dietary intervention make a meaningful difference in this condition,” Dr. Jason Fung, a nephrologist and leading expert in kidney disease and intermittent fasting, said on a recent episode of “Vital Signs” on The Epoch Times. The FMD may be easier to achieve than traditional water fasting, triggering the body’s repair mechanisms and reducing inflammation in a way that feels sustainable rather than punishing.
Although the diet is not a cure or a replacement for medical care, Fung believes that, when used thoughtfully under medical guidance, the FMD can serve as a practical, complementary tool in chronic disease management alongside conventional treatment.
What Is the Fasting-Mimicking Diet?
Longevity researcher Valter Longo and his team at the University of Southern California developed the FMD. Longo is known for his research on aging, nutrition, and fasting-mimicking diets. The diet includes plant-based foods—such as vegetable soups, nuts, olives, and herbal tea—while avoiding meat, dairy, alcohol, and processed carbohydrates.
Related Stories
Calories are sharply reduced, but not eliminated. “It’s a modified fast that can be very effective for people,” Fung said. The plan provides essential nutrients through low-calorie, plant-based foods that are very low in protein and sugars. As a result, it is intended to avoid spiking insulin or mTOR—the main pathways driving growth and metabolism—while still allowing limited eating. The goal is to keep insulin and mTOR low enough that the body shifts into repair mode, without the physical and social difficulty of a full water fast.
This low-calorie protocol delivers most of the metabolic advantages of a true fast—including cellular repair and reduced inflammation—but in a much more sustainable way.
That trade-off matters. Traditional multiday water fasts are notoriously difficult. Hunger, fatigue, and social challenges mean many people quit after one attempt. “If you just tell somebody to do five days every month with just water and tea, you know your compliance rate will just plummet after a couple of months,” Fung said. The FMD preserves most of fasting’s core benefits while being substantially easier to follow, a distinction that could make it more clinically useful.
In other words, you don’t have to follow a strict water-only fast to gain the benefits. “This is the advantage of a fasting-mimicking diet over fasting alone,” Fung added. “So if you can make fasting still preserve sort of 80 percent of the benefits, but make it 50 percent easier? Well, that’s a pretty good trade-off.”
Why the Kidneys?
Chronic inflammation drives many forms of kidney disease. By lowering inflammation and shifting the body away from constant growth signals, the FMD can help slow disease progression.
Fung is particularly excited about early research: “Any kind of chronic kidney disease might be improved by this fasting-mimicking diet—and by extension, any sort of fasting.”
“Fasting actually causes a complete change in how your body works,” Fung says. “When those nutrient sensors go down—insulin, mTOR… your body shifts to a sort of regenerative, survival mode—not growth, but maintenance mode.”
When the body enters repair mode, it conserves energy by dialing down excess inflammatory responses. “You have this whole shift into maintenance repair mode, and you’re going to have less inflammation because excess inflammation takes energy. You want to shut it down,” Fung noted. This shift can help prevent tissue damage and scarring in organs, including the kidneys.
Fasting also triggers autophagy, the body’s process of removing excess, damaged, or dysfunctional cells. “Autophagy is this idea that when you put your body into this repair maintenance mode, you’re going to get rid of some of the excess cells, excess inflammation, excess all this stuff, so there’s going to be less fibrosis and less scarring,” Fung said. In the kidneys, this could mean less fibrosis, or tissue thickening and scarring, and potentially slower disease progression.
For Fung, these results stand apart. Conventional anti-inflammatory treatments, like prednisone, can be effective but carry significant side effects. A dietary intervention that produces similar systemic effects, with fewer risks, could expand the available treatment options. “This is super exciting,” Fung said, calling it a potential breakthrough in kidney treatment.
What FMD Can and Cannot Do for Kidney Health
For people whose kidneys have already lost much of their filtering capacity, such as those on dialysis, treatment focuses on slowing further damage and managing complications rather than restoring kidney function. These people often require a highly restrictive renal diet that limits protein, carbohydrates, salt, potassium, and phosphorus because their kidneys can no longer effectively remove these substances. Such dietary restrictions are essential for controlling symptoms and preventing potentially dangerous imbalances.
The low-salt FMD is different from a traditional renal diet. Rather than simply restricting nutrients, it is designed to mimic the metabolic effects of fasting while accommodating the needs of people with chronic kidney disease. Even so, Fung emphasizes that dietary interventions alone do not reverse advanced kidney damage. Instead, they may help reduce the burden on kidneys that have already lost much of their function.
By contrast, people with healthy kidneys or early-stage kidney disease generally do not need such restrictive diets. Fung said that most people fare better with a balanced approach that includes adequate protein and nutrients.
Salt is one example. Many people assume everyone should drastically reduce sodium intake, but Fung said this is unnecessary for most people with healthy kidneys or only mild kidney impairment. “Your kidneys simply get rid of the excess. You eat it, they excrete it—no problem,” Fung noted. For the majority, Fung added, “A very, extremely low salt diet can actually stress your body and may be harmful.”
People who are salt-sensitive, sometimes because of genetic factors, are an exception and may experience substantial increases in blood pressure after eating large amounts of salt.
Where FMD may hold the greatest promise is earlier in the course of kidney disease, or even before disease develops. Rather than serving as a cure, it is best viewed as one component of a broader strategy for preserving long-term kidney function.
How Modern Diets Affect Kidney Health
Modern diets may expose people to potential hidden inflammatory triggers, from additives in processed foods to naturally occurring compounds in plants that some people are sensitive to.
“A lot of ultra-processed foods have all these chemicals. And it’s very topical right now, with discussions about banning red dye number three,” Fung said. Herbicides and pesticides, especially in large-scale monoculture grain farming, also introduce compounds into the food supply.
“Grain today is very different from what it was 50, 60, or 70 years ago,” Fung said, noting that modern grains are often grown and processed with additives that were uncommon in the past—such as red dye No. 3, a synthetic food coloring banned by the Food and Drug Administration in 2025 after studies linked it to cancer in laboratory rats.
Even everyday staples like milk can be affected. In the United States, some dairy farmers still use recombinant bovine growth hormone (rBGH/rBST) to boost milk production in cows. This practice is banned in the European Union, Canada, and several other countries due to concerns about animal welfare.
“When you react, the body responds in a very stereotyped way: inflammation,” Fung said. In organs like the kidneys, repeated inflammatory responses can lead to scarring that progressively impairs function.
There’s No Universal Fasting Schedule
Fasting takes many forms—intermittent daily fasts, 24-hour fasts, seasonal fasts, and extended multi-day cycles. The power of the FMD lies in its ability to activate key repair and regeneration pathways that everyday eating suppresses. Constant food intake, particularly frequent meals rich in carbohydrates and protein, can maintain elevated levels of insulin and mTOR. These two key signaling pathways promote growth and energy storage but can actively inhibit autophagy, repair, and metabolic reset.
Fung does not prescribe a single fasting protocol. He tailors recommendations to individual patients, adjusting them based on a person’s response, lifestyle, and goals. Some do well with 16-hour daily fasts. Others prefer 24-hour fasts two to three times a week. The five-day FMD cycle is particularly useful for patients who need the deeper cellular repair benefits that shorter fasts don’t fully activate. “You’re getting a huge bang for your buck because you’re hitting a different pathway completely. Therefore, you’re getting the maximum benefits of what you’re trying to do.” Fung said.
His own approach combines several methods: regular 16-hour fasts, occasional 24-hour fasts, and periodic five-day cycles. He also adjusts the protocol to improve tolerability. For the first two days of a longer fast, he sticks mostly to water and green tea; from day three onward, he adds a few vegetables to make it easier to continue. “I basically stick to boiled or stir-fried vegetables—broccoli, bok choy, Napa cabbage, that kind of thing. I take them once a day while I’m fasting. It’s quite individual.”
The Bigger Picture
For Fung, the promise of FMDs lies in how they fit within a broader approach to chronic disease. They may not be a cure, but they could offer a low-cost, accessible, and biologically plausible way to support the body’s repair systems.
“Fasting itself has been around for 1000s of years,” he said. “There’s the relatively low risk to doing these sorts of interventions, and potentially a benefit in terms of chronic kidney disease that would add to any other benefits you know, of any of your other treatments.”
In a world where chronic diseases are increasingly common, that is a compelling proposition: a simple intervention that may help the body do what it is designed to do—slow down, repair [itself], and restore balance.
