Fasting-mimicking diet promises to reduce biological age and extend life

A fasting-mimicking diet is what it says: it only mimics; there’s no absolute fasting involved. Yet the diet provides the benefits of fasting without having to fully abstain from food. It helps with weight loss, reduces inflammation, and supports metabolic health.

The most appealing claim is the ability to reduce the body’s biological age by three years. That is what researchers at the University of Southern California Leonard Davis School of Gerontology say after a two-and-a-half-year study.

“[FMD] is making the system younger, and by making it younger, making it more functional,” Dr Valter Longo, director of the USC Longevity Institute, tells Fortune. “It’s really repairing the problem from the source, rather than just putting a Band-Aid downstream of it.”

A fasting-mimicking diet, also known as a fast-mimicking diet, is low in calories, carbohydrates and protein and allows the consumption of certain types and amounts of food. “It’s designed to mimic fasting without fasting,” says Dana Ellis Hunnes, a senior clinical dietitian at UCLA Medical Centre and assistant professor at the UCLA Fielding School of Public Health in Los Angeles.

The diet tricks the body into thinking the person is fasting, but, in reality, some food is eaten. Popularised by Dr Valter Longo, a biogerontologist and cell biologist, the diet has been around since the mid-2010s but has gained plenty of interest recently.

What’s a fasting-mimicking diet?

It’s a dietary protocol designed to mimic the effects of a prolonged fast while providing some nutrient intake. A typical FMD diet includes plant-based foods such as vegetables (soups), leafy greens such as kale, collard, spinach, nuts, seeds and healthy fats like olive oil.

The diet could last from 4 to 7 days, and it can be repeated every few weeks or months, according to Medical News Today. The calories and subsequent macronutrient goals will vary from person to person, depending on the regular food intake.

How is FMD different from intermittent fasting?

Intermittent fasting takes different forms. The 16:8 method allows for a daily 8-hour window to eat, while another approach involves fasting one or two days per week. In all forms, intermittent fasting dictates when to eat.

The FMD is generally a 5-day diet [See diet plan below] high in unsaturated fats and low in overall calories, protein, and carbohydrates. It mimics the effects of a water-only fast while providing necessary nutrients. So people find it easier to complete the fast.

How does the fasting-mimicking diet work?

It relies on a specific breakdown of macro- and micronutrients. Here’s a five-day diet, according to the US News and World Report.

Day 1: About 1,100 calories are consumed: 11% are from plant-based protein, 46% from mono- and polyunsaturated fats and 43% from complex carbohydrates (rich in fibre).

Days 2 to 5: About 725 calories per day, with 9% protein, 44% fat and 47% carbohydrates.

During each of the five days, a minimum of 2 litres of water is consumed. The fast period should be repeated once per month for the first three consecutive months to achieve optimal results, says Kristine Dilley, a registered dietitian at the Ohio State University Wexner Medical Centre in Columbus.

Is the fasting-mimicking diet safe?

According to current research, a fasting-mimicking diet for five days a month is safe and effective but has some side effects.

Individuals may experience:

What are the other risks?

Since the fasting-mimicking period only lasts five days, results will not be sustainable, says UCLA dietitian Hunnes. “For diet results to be sustainable, you need to be following a lifestyle diet or change for several months, if not years,” she says in a report in the US News and World Report. “This is setting you up for yo-yo dieting and weight loss/regain.”

Lack of food denies the body of calories, which could slow your metabolic rate, leading to a starved feeling, Hunnes adds.

Dehydration is another risk as there’s a limitation in food intake. “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,” Ohio dietitian Dilley says.

Who can follow a fasting-mimicking diet?

A fasting-mimicking diet can be helpful for individuals who want to manage their body weight and improve their overall health, a report in Healthline website says.

As with any diet, a health expert’s supervision is essential. Because people with certain medical conditions and women who are pregnant or breastfeeding shouldn’t follow this diet.

Who should avoid the fasting-mimicking diet?

■ Women who are pregnant or breastfeeding

■ People who are underweight, malnourished or fighting an infection

■ Children younger than 18 years old and adults over the age of 70

■ People with eating disorders

■ Avoid strenuous activities or working outdoors in high temperatures

■ Individuals with health conditions such as diabetes, hypertension,

■ Liver disease or other chronic conditions

■ People on medications should follow medical advice.

Can the diet help lower biological age?

The chronological age indicates how long a person has been alive, and the biological age reflects the age of cells and how well the body is functioning. The two numbers need not match, and research suggests that biological age is the better predictor of mortality risk, according to a report in Fortune.

Individuals following the diet for a total of 15 days a year could turn back the internal clock by nearly three years, according to the findings of a study published in the journal Nature Communications. Researchers at the University of Southern California Leonard Davis School of Gerontology studied people who completed three monthly diet cycles and showed a 2½-year decrease in median biological age.

What the critics say

One criticism levelled against the diet is the expense. Five days of dieting followed by three weeks of unrestricted eating make it expensive.

“The hefty price tag may be prohibitive for many to be able to stick with the diet long enough to show benefits,” dietitian Dilley says.

“It seems to be another fad diet that most likely isn’t worth its high price tag,” UCLA dietitian Hunnes adds.

Others say more research is needed to determine the ideal length and frequency for a fasting-mimicking diet.

What research says

The diet reduces signs of immune system ageing, insulin resistance, and liver fat in humans, resulting in a lower biological age, according to the USC Leonard Davis School of Gerontology-led study developed by Longo, the senior author of the study.

“This study shows for the first time evidence for biological age reduction from two different clinical trials, accompanied by evidence of rejuvenation of metabolic and immune function,” Longo says.

Previous research led by Longo has suggested that “FMD cycles are associated with a range of beneficial effects, including the promotion of stem cell regeneration, lessening of chemotherapy side effects, and reduction of the signs of dementia in mice, as well as the lowering of the risk factors for cancer, diabetes, heart disease and other age-related diseases in humans,” according to a report in the USC Leonard Davis website.

A study by Sebastian Brandhorst, USC Leonard Davis research associate professor, and Morgan E. Levine, founding principal investigator of Altos Labs and USC Leonard Davis PhD alumna, also highlights the FMD’s potential as a dietary programme capable of reducing their disease risk and improving their health without significant lifestyle changes, Longo said.

Does FMD really work?

Longo is sure of the benefits of a fasting-mimicking diet, but others are sceptical. Dietitians say these benefits can be derived from other diets as well. Whatever the facts, it’s always best to seek professional medical advice before starting any diet. After all, health is wealth.