Khyra put on weight normally until April 2007, the court heard
A seven-year-old girl who was allegedly starved to death by her mother had lost about 40% of her body weight by the time she died, a court was told.
Khyra Ishaq's body mass index at the point of her death in May 2008 "ran off the scale" of normal medical charts, Birmingham Crown Court heard.
Professor Peter Milla said the girl's condition was "extremely unusual".
Khyra's mother Angela Gordon, 34, and Junaid Abuhamza, 30, both of Leyton Road, Handsworth, deny murdering Khyra.
Mr Abuhamza pleaded guilty last week to five cruelty charges relating to other children.
Ms Gordon denies the charges of child cruelty, which are alleged to have been committed between December 2007 and 17 May 2008.
Prof Milla, a specialist in paediatric nutrition, said medical records showed Khyra had grown and put on weight normally until April 2007, when she weighed 3st 9lb (23kg).
But he said Khyra became "amazingly thin" after suffering dramatic and significant weight loss.
Asked by prosecutor Timothy Raggatt QC to comment on the child's condition, Prof Milla said: "In a child with no disease state, that is extremely unusual.
"I don't think that previously I have ever seen something as marked as that."
The physician said he had seen such weight loss in disease-free children in the developing world, but never before in Britain.
He said: "In my experience, mothers are usually very concerned when they have any reason to believe that their children are not putting on weight or growing in a normal manner.
"It must have been very clear in the week before her death that all was not well.
"In the few days before her death, the symptoms were such that most mothers would have been dialling 999 or taking her to the accident and emergency department."
Prof Milla said Khyra's physical state meant she could have been malnourished for a number of months.
He said: "Given that she was taken out of school and one of the reasons given was that she was stealing food from other children, the suspicion is that it could have been going on for some considerable while."
Prof Milla told the jury that the child's condition would have been obvious for a number of weeks.
He said: "I think she must have had an inadequate intake over a number of months."
Referring to knowledge gained from studies of IRA hunger strikes, Prof Milla added: "She (Khyra) has lost approximately 40% of her body weight - we know from the Belfast fasters that when you lose that amount of weight, you die."
The prosecution alleges Ms Gordon and Mr Abuhamza murdered Khyra by starving her "for weeks or possibly months" at her home in Leyton Road.
The trial continues.