Dietary (poly)phenols in the stimulation of energy expenditure. AMPK, 5′-AMP–activated protein kinase; BAT, brown adipose tissue; COMT, catechol-O-methyl transferase; PGC-1α, PPAR-γ coactivator-1α SIRT1, sirtuin 1; SNS, sympathetic nervous system; WAT, white adipose tissue.