An obsession with eating healthy could be bad for your health, scientists warn.

Those who deny themselves entire food groups or worry too much about the "purity" of their meals are risking their mental and physical well-being.

Experts have reported a rise in such extreme behavior, which is known as orthorexia nervosa. Sufferers of orthorexia nervosa tend to be over 30, middle class and well-educated.

Orthorexia patients are different than anorexia patients, who restrict the quantity of food they eat. Sufferers of orthorexia, named after the Greek word for "right or true," fixate on quality.

Sufferers often eliminate sugar, salt, caffeine, alcohol, wheat, gluten, yeast, soya, corn and dairy foods from their diet. Foods tainted by pesticides or that contain additives such as MSG may also be ditched. Such habits may seem quirky, but they can have a serious effect on health.

Cutting out entire food groups can leave sufferers malnourished, while rigid rules can make eating out impossible, putting a huge strain on friendships and relationships.

"I am definitely seeing significantly more orthorexics than just a few years ago,” said Ursula Philpot, chairman of the British Dietetic Association's mental health group. "Other eating disorders focus on the quantity of food, but orthorexics can be overweight or look normal.”

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