Excessive exercise, like extreme diets, attracts people who feel an extreme need for control in their lives.

Quite early there came the contradiction that anyone who takes on an extreme diet must meet.

She is not on any extreme diet, but she is being taught to eat healthily for the rest of her life.

This is not to say that extreme diets have disappeared.

"The extreme diet is unrealistic," said Sherman this week.

Worst of all, extreme diets like the Master Cleanse can cause serious side effects in vulnerable groups.

While a really extreme low-calorie diet - 500 calories or so - could be risky, nobody can really stick to that anyway.

(Fassbender went on an extreme, 600-calorie-a-day diet to drop the necessary weight).

But you should be wary of any extreme diets that make amazing claims, like "curing psoriasis," since they won't work.

The findings underscore the dangers of the disorder, in which people go on extreme diets.