Valter Longo

PhD · Edna M. Jones Professor of Gerontology and Biological Sciences and director of the Longevity Institute, USC Leonard Davis School of Gerontology · author of The Longevity Diet

Go-to expert for: fasting-mimicking diet and longevity eating

Who and why

Valter Longo is a biochemist who directs the Longevity Institute at the University of Southern California and also leads a longevity and cancer programme at IFOM in Milan. He developed the fasting-mimicking diet, a five-day low-calorie plan designed to give some of the effects of fasting while still eating, and tested it in clinical trials. His book The Longevity Diet sets out a mostly plant-based everyday eating pattern alongside these periodic fasting cycles.

Why it matters after 50: What and when we eat affects weight, blood sugar, blood pressure and the risk of the main diseases of ageing. Longo's work also shows that protein needs change around 65, when eating too little protein can speed up muscle loss and frailty.

What Longo recommends

Eat mostly plants with some fish: legumes, whole grains, vegetables, nuts and olive oil, with fish no more than two or three times a week. Limit red and processed meat, sugar and refined grains.Some evidence
Under 65, keep protein low but sufficient: about 0.7 to 0.8 g per kg of body weight per day, mainly from plant sources such as beans and lentils.Some evidence
After 65, eat slightly more protein, adding fish, eggs, white meat and goat or sheep products, to help keep muscle. He does not give a fixed number for this age group.Some evidence
Fit all meals into a window of about 12 hours a day, and stop eating 3 to 4 hours before bedtime.Personal habit
A five-day fasting-mimicking diet (roughly 700 to 1,100 calories a day) lowered weight and blood pressure in trials; blood sugar and inflammation improved mainly in people who started with risk factors. Longo says to see a doctor before trying it and to be supervised; most healthy people would repeat it every three to six months. It is not for people taking insulin or metformin, or with a BMI under 18.Doctor only

Signature: The fasting-mimicking diet (five days, a few times a year)

A five-day plant-based plan of soups, bars, drinks and snacks that is low in calories, protein and sugar, designed to mimic fasting while still eating. It is sold commercially as ProLon and is usually done in cycles every one to several months, depending on a person's health.

In your plan

Choose him for eating: protein stays at least 1.2 g per kg (you can choose 1.0). A fasting-mimicking week becomes a light training week, and it is off at 70+ unless your doctor agrees.

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Research and honest caveats

Fasting-mimicking diet trial

In 100 mostly healthy adults, three monthly five-day cycles reduced weight, body fat, blood pressure and IGF-1 compared with a normal diet; blood sugar, cholesterol and the inflammation marker CRP improved mainly in people who started with risk factors (post hoc analysis).

Wei et al., Science Translational Medicine, 2017

Protein intake and mortality by age

In over 6,000 US adults aged 50 and older, high protein intake (mainly from animal sources) was linked to higher cancer and overall death rates at ages 50 to 65, but moderate to high protein was linked to better health after 65 (an observational study).

Levine et al., Cell Metabolism, 2014

Longo founded L-Nutra, the company that makes ProLon and supplies the food used in many of his fasting-mimicking diet trials; USC also has an ownership interest, and he says he donates his consulting fees, book royalties and most of his shares to charity. The trials are relatively small and short, and his protein findings come largely from observational data.

Career highlights

2014Led a large study linking high protein intake to higher mortality before 65 but not after
2017Published the main randomised trial of the fasting-mimicking diet in 100 adults (pilot results appeared in 2015)
2018Published The Longevity Diet and was named one of Time's 50 Most Influential People in Health Care
2024Reported that three fasting-mimicking diet cycles lowered estimated biological age (median about 2.5 years) in a small trial