A 700-pound woman is starting an urgent battle to lose weight so she can fit in a brain scan machine.

Terri Smith, 49 — thought to be the fattest woman in the world — is trapped in her bedroom in Cleveland, Ohio, US, unable to move, stand or roll over by herself.

She suffers severe headaches and needs an MRI scan to check for a potential brain tumor but is too big to fit in a scanner or through the doors of a hospital.

"My husband is my guardian angel. He's stuck by me through everything. Most men would have left a long time ago, and who could blame them — but Myron is a living saint," Smith said.

She faces a race against time to lose weight in a bid to qualify for gastric surgery.

Smith, who has been bed-bound for three years, said, "People must think, 'How could you let yourself get like that?'

"It's awful how it creeps up on you. Once you cannot exercise it doesn't matter how healthily you eat, the weight just sticks. You're not burning off a single calorie."

Dr Dariush Saghafi said, "Caring for someone of Terri's size is very difficult. It is very hard to move and transport her.

"Hospitals do not have equipment to hold someone of her girth.We thought that it might be possible for Terri to have an MRI at the Cleveland Zoo in the machine used for the elephants and rhinos but the zoo does not have a license for humans."

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