IU had previously revealed that she went on a diet for her comeback.
Her diet involved one apple, one sweet potato, and one protein drink per day, as well as an hour of aerobic exercise.
On October 31st, she appeared on 'Happy Together 3' and explained that diet was just used as an extreme measure, but she is eating well now.
According to All Kpop, It appears the extreme measure paid off as she revealed, "During a four day period, I lost 4 kg.
"That is really extreme. I exercised diligently and ate small amounts."
It is a good thing it was for a relatively short period of time and IU is now back to eating normally.