By Alex Trickett BBC Sport Online

Teetotal Tony McCoy has opted for near-starvation rations to make the weight for a crucial race at Cheltenham on Saturday.

The Ulsterman has told the Racing Post that he's living off one piece of chicken, a Jaffa Cake and some vitamins per day to slim down to his ideal racing weight of 10st 1lb.

But according to Jacqueline Boorman, accredited sports dietician and consultant to the British Olympic Committee, McCoy may be doing himself serious damage.

"In terms of nutrition, clearly this crash diet is not adequate," she told BBC Sport Online.

"Eating in this way will impair his health and batter his immune system. He is putting his organs under threat."

Boorman, who has worked with many British athletes and rowers, accepts that making weight in sport is not an easy business.

"It is a very complex area nutritionally and psychologically," she said.

"If McCoy has been successful in the past, it is understandable that he sticks with what he knows.

"The chicken gives valuable protein and the Jaffa Cake adds a few carbohydrates.

"They are probably foods he trusts and, on a crash diet, not everything is tolerated by the gut."

"At the British Olympic medical centre, we have a number of athletes who suffer from 'Under Recovery Syndrome'.

"They can't get over coughs or colds and this could also apply to jockeys like McCoy, who crash diet when they have no excess fat to lose."

But, for punters looking to back McCoy's mount Chicuelo this weekend, potential health hazards need not compromise performance.

"Frustratingly for everyone else, the right way does not always prevail," says Boorman.

"Skill, psychology and determination can counterbalance poor diet. People do fantastic things under extraordinary circumstances and they do win.

"What McCoy is doing is not sensible, but few things in top-level sports are."