The 30-year-old star has been training at a specialist gym where clients are put through punishing regimes that act like a "natural Botox" to fight off ageing.
Lily posted a photograph of herself at the Face Gym in central London alongside the caption, "Putting in the hours @face_gym #tiring (sic)."
Customers are offered half-hour 40 pound treatments which include a warm-up, cardio, advanced training and a cool down.
They can also seek help for specific problem areas including the scalp, brows, cheeks and jaw.
The "Hard Out Here" singer has signed up for the training sessions two months after celebrating her 30th birthday in May.