“The data suggest that our metabolisms don’t really start to decline again until after age 60. The slowdown is gradual, only 0.7% a year. But a person in their 90s needs 26% fewer calories each day than someone in midlife.
Lost muscle mass as we get older may be partly to blame, the researchers say, since muscle burns more calories than fat. But it’s not the whole picture. “We controlled for muscle mass,” Pontzer said. “It’s because their cells are slowing down.”
“All of this points to the conclusion that tissue metabolism, the work that the cells are doing, is changing over the course of the lifespan in ways we haven’t fully appreciated before,” Pontzer said. “You really need a big data set like this to get at those questions.””