20–60the ages it held level, on averageMOSTLYSupported

Does Metabolism Slow With Age? Yes — at 60, Not 30

Line chart of energy expenditure across the lifespan: a peak in infancy, flat from age 20 to 60, then declining

6,421 people across 29 countries, measured by doubly labelled water: energy expenditure is flat from 20 to 60, even during pregnancy. It falls about 0.7% a year after that. The decline is real — it just starts four decades later than everyone thinks.