Metabolism may not slow after age 20, so why do we still gain weight?

For a long time, it was believed that after the age of 20 your metabolism decreased dramatically—making it harder to lose weight and keep in shape. But a recent study has shown our metabolism—also known as energy expenditure—stays relatively stable between the ages of 20 and 60, before decreasing at older ages.

source https://medicalxpress.com/news/2021-08-metabolism-age-gain-weight.html