The 'Womanizer' hitmaker - who has sons Sean Preston, five, and four-year-old Jayden James with ex-husband Kevin Federline - claims running after the tots every day has encouraged her to be more active in everyday life.

She said: "How do I keep slim? Having two boys definitely helps, and I love to dance. It's the best way to stay in shape."

Though she loves looking after her children, Britney also loves have time to herself and lives to reward herself with indulgent beauty treatments.

She explained: "I love treating myself to a spa day. Massages are my favourite."

The 'Radar' singer also revealed she enjoys varying her make-up style each day depending on her mood.

She said: "Sometimes I keep it simple and don't wear much make-up - just a little mascara and lipgloss. Other times, I'll play around and do heavier make-up or some fun lipstick."

When it comes to beauty icons, Britney always turns to Madonna for ideas in revamping her appearance.

She said: "I love, love, love Madonna! She's one of my inspirations."