But the 22-year-old singer has assured everyone that she had lost weight because doctors had discovered the heart murmur.
"I found out about three months ago. I have been asthmatic all my life but this was really quite scary," The Sun quoted her, as saying.
"When they asked me how much exercise I did, I had to be honest and say hardly any. Now I make sure I work out three times a week. And I don't hold back — it's a hardcore routine in the gym," she added.
A heart murmur is often quite harmless, but it sometimes can indicate a hole in the heart or a valve problem. In order to help the heart muscles stay fit and cope with the condition, exercise is the best remedy.
"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. I'd devour the lot," she said.
She told a magazine: "I haven't done this because I want to be some skinny minnie. I just like being more toned. It has made me really happy. I should give up smoking but haven't quite managed that yet."