Lily Allen has revealed she lost weight because doctors discovered she had a heart condition.

The 22-year-old singer sparked concern when she dropped from a size 12 to an eight in just six weeks.

But the Smile star said the weight came off when she was told the "scary" news.

She told a magazine that she learned she had an irregular heart murmur three months ago and has since been hitting the gym to ensure she gets plenty of exercise.

Allen said: "I make sure I work out three times a week now, and I don't hold back."

She also added that she's had to cut back on junk food, drinking and would like to give up smoking but "haven't quite managed that yet".

A heart murmur is often harmless but can also indicate a hole in the heart or a heart valve problem.

Allen, who is dating Chemical Brother Ed Simons, 37, recently revealed she wants to make only one more album before retiring at 25 to start a family.