Miley Cyrus dates actor Liam Hemsworth

Miley Cyrus looked ultra slender as she left a Pilates class in LA yesterday.

The once curvy US star displayed a super-flat stomach and long, skinny legs in black leggings and a crop top.

Her slimmed-down look has prompted speculation that the 19-year-old has an eating disorder - but she was quick to rubbish the rumours and explain her new frame.

'For everyone calling me anorexic I have a gluten and lactose allergy. It's not about weight it's about health. Gluten is crapppp anyway!' Tweets Miley.

The star also posted a photo of herself with a bag of fast food, which she was sniffing for enjoyment because she 'can't eat it'. 

'Everyone should try no gluten for a week! The change in your skin, phyisical and mental health is amazing! U won't go back!' writes Miley.

Despite Miley's words, dietitians and nutritionists warn that a gluten-free diet - which omits grains such as wheat and barley - can be detrimental to a person's health if they're not genuinely allergic.

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Esme Riley