After examining over 350 papers, researchers at University of Wisconsin-Madison in the United States concluded that reducing protein, or limiting certain amino acids within it, may improve metabolic health and slow some biological processes associated with aging. In several animal studies, these dietary changes also extended lifespan. 

Scientists have known that restricting calories can extend lifespan in organisms ranging from flies to rodents. Calorie restriction also reduces the incidence of several age-related diseases in lab animals. Protein restriction may trigger the same protective responses without requiring a reduction in total calories.