Los Angeles (LabNews Media LLC) – A low-protein diet enriched with the amino acid methionine can extend healthy lifespan, reduce fat mass, and lower the risk of frailty in mice. This is shown by a study from the University of Southern California, published in the journal Cell Metabolism (DOI: 10.1016/j.cmet.2026.05.015).
The so-called "Longevity Diet" is based on the traditional diets of long-lived populations, such as those in Southern Italy or Okinawa. These diets are predominantly plant-based and contain little animal protein. However, too low methionine levels can lead to frailty. By targeted supplementation with methionine, the positive effects of the low-protein diet could be maintained while avoiding the negative consequences.
In the study, older mice received different diets, including a high-calorie Western diet, a ketogenic diet, and the modified Longevity Diet. The methionine-enriched version led to a significant improvement in metabolic parameters, an increase in signaling molecules such as GLP-1, growth hormone, and FGF21, as well as less fat mass and reduced frailty – even though the animals consumed more calories than in other groups.
An analysis of data from over 200,000 people supported these findings: Higher consumption of animal protein (and thus higher methionine intake) was associated with an increased risk of obesity and type 2 diabetes.
"It's not just the total amount of protein that matters, but primarily the composition of amino acids," explained Maura Fanti from the USC Leonard Davis School of Gerontology. Valter Longo, one of the senior authors, emphasized that the results challenge the notion that weight loss must necessarily be accompanied by calorie reduction.
The researchers are now planning controlled clinical trials in humans to verify the results. The study underscores the importance of precise control of amino acid intake for promoting healthy aging.
