Energy balance

Declining brown adipose tissue (BAT) activity with age contributes to reduced energy expenditure and increased obesity risk, mediated by reduced sympathetic output and increased FOXA3 transcription factor.

Brown fat, which burns calories to generate heat, becomes less active as you age. This is partly due to reduced nerve signals and changes in gene expression. While you cannot easily reverse this biological change, maintaining physical activity may help stimulate remaining brown fat function.