The Spice Girl dismissed speculation that she maintains her trim physique by refusing to eat, saying she prefers to burn calories in the bedroom.
She told OK!: "Some women ask if I'm so thin because I shag all day.
"And I say, 'Actually, yes! And I bet you would too if you were married to David Beckham'."
It was recently reported that David is "wild with jealousy" over his wife's flirtatious behaviour.