Kelly Clarkson across the years and her weight gain. In 2002 Kelly Clarkson weighed about 120 pounds (54kg) and now, in 2009 she weighs about 180 pounds (81kg). The causes for her weight gain were: poor diet and she don't like to do exercises. Besides this, Kelly loves food, especially fast food and candies. She gained about 60 pounds (27 kg). (less info)