Partly, according to small trials. The fasting mimicking diet (FMD) is a five-day, low-calorie, low-protein, plant-based eating plan done about once a month. In a randomized trial, three monthly cycles lowered weight, body fat, blood pressure and IGF-1, a growth hormone linked to aging. A later analysis estimated it lowered "biological age" by about 2.5 years. But the trials are small and short, the biological-age figure is an estimate, and the diet's inventor owns the company that sells it.
- SymptomRising weight, blood pressure and metabolic risk
- Before thatGrowth signals stay high, repair stays low
- Before thatIGF-1 and mTOR rarely switch down
- RootThe body almost never experiences a fasting state
What the fasting mimicking diet is
Long water fasts are hard, and they can be risky. Researcher Valter Longo and his team asked: could you get some of fasting's effects while still eating? The result is the fasting mimicking diet (FMD): five days of low-calorie, low-protein, low-sugar, plant-based food, mostly soups, nuts, olives and herbal teas, then back to normal eating for the rest of the month.
The idea: by keeping protein and sugar very low, the body's growth signals drop much as they would during a fast, even though you're still eating some food.
The upstream target: IGF-1
One of those growth signals is IGF-1 (insulin-like growth factor 1), a hormone, or chemical messenger, that tells cells to grow and divide. During childhood, that's exactly what you want. In adulthood, research in animals links lower growth signaling to longer life, and very high IGF-1 in humans has been linked to some age-related diseases. Fasting lowers IGF-1. So does a very low-protein diet. FMD combines both for a few days at a time.
What the human trials found
Three monthly cycles: weight, blood pressure, IGF-1
A · 100 adultsHealthy adults were randomly assigned to three monthly FMD cycles or to eat normally. FMD lowered body weight, body fat, blood pressure (by about 4.5 points systolic, more in people with high readings) and IGF-1. No serious side effects were reported.[1]
"Biological age" down about 2.5 years
B · Exploratory analysisA later analysis of blood tests from two FMD trials found lower insulin resistance (the body responding poorly to insulin), less liver fat, and an estimated 2.5-year drop in biological age based on seven routine blood markers.[2] Interesting, but this was an after-the-fact analysis of 86 people, not a direct test of aging.
Five days a month makes you 2.5 years younger.
Three cycles lowered several risk markers, and an estimate based on blood tests improved. That's promising, but it's not the same as living longer.
The fine print
- Small and short. Trials ran for three months with around 100 people. We don't know long-term effects.
- Conflict of interest. Valter Longo founded and has an ownership stake in L-Nutra, the company that sells the commercial FMD kits used in these studies. That doesn't make the results wrong, but independent trials matter.
- Healthy, motivated volunteers. People who sign up for diet studies are often healthier than average, which can make results look better.
- Weight loss explains part of it. Losing weight alone improves blood pressure and blood sugar; how much extra FMD adds is still being worked out.
How it compares
Fasting mimicking diet
B · Small trialsEasier than water fasting; promising effects on risk markers.
Everyday calorie restriction
A · Small effect on aging paceEating a bit less every day slowed one measure of aging in a two-year trial. See does intermittent fasting slow aging?
Multi-day water fasts
C · Mostly animalStronger effects in animals, more risks in people. Only under medical supervision.
The bottom line
The fasting mimicking diet is one of the better-studied fasting approaches, and its early human results on weight, blood pressure and IGF-1 are real. But it's not proven to slow aging, the trials are small, and the science comes largely from the people who sell it. If it appeals to you and your doctor agrees, it's a reasonable experiment. If not, a modest daily calorie reduction and regular exercise cover much of the same ground. For the cleanup side, read how long you have to fast for autophagy.
Frequently asked questions
How does a fasting mimicking diet work?
It provides about 700 to 1,100 calories a day for five days, mostly from vegetable soups, nuts and olive oil, with very little protein and sugar. That combination lowers growth signals in a way that resembles fasting, while still allowing some food.
How often should you do a fasting mimicking diet?
Studies used one five-day cycle per month for three months. Long-term schedules haven't been well tested. Talk to your doctor first, especially if you take medication.
Can I make my own fasting mimicking diet?
Many people try home versions based on the published approach. They haven't been tested in trials, and it's easy to get the protein or calorie balance wrong. If you try it, keep it short and get medical advice first.
Who should not do a fasting mimicking diet?
People who are pregnant or breastfeeding, underweight, have diabetes treated with medication, have a history of eating disorders, or are frail should not do it without medical supervision.
Sources
- Wei M, et al. Fasting-mimicking diet and markers/risk factors for aging, diabetes, cancer, and cardiovascular disease. Science Translational Medicine, 2017.
- Brandhorst S, et al. Fasting-mimicking diet causes hepatic and blood markers changes indicating reduced biological age and disease risk. Nature Communications, 2024.