Lily AllenLily AllenLily Allen's shared a v personal secret.

It's all about how she dropped some poundage, and it ain't what you think.

In an interview with Grazia magazine Lil's revealed that she lost weight because doctors discovered she had a heart murmur.

She shrunk from a size 12 to a size eight in just six weeks.

She's told Grazia: "I found out I had a heart murmur about three months ago.

"I had switched doctors and just went for a routine check up, which is when they discovered I had this irregular murmur.

"I have been asthmatic all my life, but this was really quite scary. When they asked me how much exercise I did, I had to be honest and say hardly any."

She went on to say: "I make sure I work out three times a week now, and I don't hold back. It's a hard-core routine and I'm usually in the gym for at least an hour-and-a-half.

"I used to love nothing more than sitting in front of the telly with two packets of Ginger Nuts and two bags of milk bottle sweets - and I'd devour the lot.

"But this heart thing has made me cut back on all that kind of crap. I now find that, because I am looking after myself, I don't feel like eating the bad stuff so much."

She's also said: "I really want to stress that I haven't done this because I want to become some skinny minnie - I will never be like that.

"I just like being more toned, it has made me really happy and I know I will never be super skinny because I would never be happy."