Protein has become a cornerstone of modern fitness advice, with high-protein diets commonly promoted for muscle building, weight management and healthy ageing. But new research suggests that eating less protein could offer certain metabolic and longevity benefits, particularly for relatively sedentary people.
A research review led by Dudley Lamming of the University of Wisconsin-Madison examined around 350 scientific papers investigating protein restriction and ageing.
The findings suggest that the relationship between protein and health is more complicated than simply assuming that more is always better.
Lamming noted that protein clearly benefits muscle growth and the body’s response to exercise in physically active people. However, he suggested that many relatively sedentary adults could be consuming more protein than they require.
Lower Protein Intake Linked to Weight and Blood Sugar Benefits
Previous animal research has shown that restricting protein can extend lifespan in flies and rodents, even without reducing their overall calorie intake.
More recently, clinical trials involving humans have suggested that reducing dietary protein may lead to improvements in several metabolic measures.
Researchers reported associations with lower body weight, reduced fat mass and improved fasting blood sugar, even in some cases where participants following protein-restricted diets consumed more total calories.
However, this does not mean high-protein diets are necessarily harmful.
When combined with regular exercise, higher protein consumption can support weight loss, muscle development and preservation of muscle mass, particularly among older adults who are vulnerable to age-related muscle loss.
How Could Protein Restriction Affect Ageing?
The researchers identified several biological mechanisms that could potentially explain the benefits observed with protein restriction.
Lower protein intake may influence how cells detect and respond to nutrients, improve metabolic processes, reduce certain forms of cellular damage and help preserve healthy cellular function.
One hormone receiving particular attention is fibroblast growth factor 21 (FGF21).
FGF21 levels tend to increase when dietary protein intake is reduced. The hormone has been linked to increased energy expenditure, improved blood glucose regulation and reduced inflammation.
Animal studies have found that mice with elevated FGF21 levels can live longer, although researchers noted that the longevity effect appeared stronger in male mice than females.
Protein restriction has also been shown to increase FGF21 levels in humans, although more research is required to establish whether this translates into meaningful increases in human lifespan.
Should You Start Cutting Protein?
The findings should not be interpreted as a recommendation for everyone to drastically reduce protein consumption.
Protein remains essential for maintaining muscles, bones, tissues, enzymes and numerous other biological functions. Requirements also vary considerably depending on age, physical activity, overall health and individual goals.
Athletes, physically active adults and older people trying to preserve muscle mass may benefit from different protein intakes than sedentary adults.
Rather than treating either high-protein or low-protein diets as universally healthier, the research highlights the importance of matching protein intake to an individual’s actual nutritional and activity needs.
Further long-term human studies will be needed to determine whether the longevity benefits observed in laboratory animals can be replicated in people.
