A diet that allows you to eat more and lose fat

A low-protein diet enriched with a precisely calibrated dose of the amino acid methionine following Mediterranean principles reduces fat mass, improves metabolism, and slows signs of aging — all without any calorie counting. This is the conclusion reached by scientists at the University of Southern California together with colleagues from the University of Toronto and Harvard. The results were published in the journal Cell Metabolism.

First author of the study Mauro Fanti and Professor Valter Longo tested the so-called LPMM diet on elderly mice aged 20 months. Remarkably, the animals ate even more food than their counterparts in the control group — yet lost fat mass and showed significantly fewer signs of aging. Levels of hormones GLP-1 and FGF21, directly linked to metabolism and longevity, were noticeably elevated in the test subjects.

Methionine is an essential amino acid found in particularly high amounts in meat, fish, and eggs. However, its content in the diet turned out to be a true "sweet spot": too little methionine — and the body faces weakness and bone fragility; too much — and the protective effect of the diet is completely lost. The decisive factor turned out to be not the overall amount of protein, but specifically its amino acid composition.

"Amino acid composition, not simply the amount of protein, determines the body's metabolic response," emphasized Mauro Fanti.

"Too little methionine — fragility, too much — and all the benefits disappear," added Valter Longo.

Alongside the mouse experiments, the authors analyzed data from more than 200,000 people. It turned out that lower consumption of animal protein correlated with a twofold lower incidence of obesity and type 2 diabetes. However, a fully plant-based diet also carries its own risks — when methionine is insufficient. The scientists emphasize: what matters is the precise balancing of protein sources, not simply eliminating meat products.