Kelly Clarkson Reveals Thyroid Issue and 37-Pound Weight Loss The singer co-hosted an hour of 'Today' and discussed her fluctuating weight and explained that she suffered from an autoimmune disease and a thyroid problem since 2006. She also credited the book The Plant Paradox for "understanding food," leading to her 37-pound weight loss. Kelly Clarkson, on "Today" She admitted she still eats what she wants but the ingredients have changed. The 36-year-old said there is one major problem with her new diet. Kelly Clarkson, on "Today" Kelly Clarkson, on "Today"