Ex-Home and Away star Sharni Vinson looks scary-skinny in a bikini

Sharni Vinson describes herself as an "exercise junkie" but these photos of the Aussie actress hitting the beach with her buff boyfriend Kellan Lutz have many fans worried that she's taken the body obsession too far since her move to the States.

The former Home and Away star was snapped on holidays in Florida with her Twilight boyfriend, fresh from filming her new movie Bait 3D.

Sharni was slim when she played Cassie on Home and Away, but the visible ribs and protruding hip bones in these latest photos are a far cry from the healthy beach bodies of Summer Bay.

28-year-old Sharni has been dating 27-year-old Kellan since September last year.