Noticed how Kelly Clarkson is looking a little slimmer these days? It's not the result of CrossFit or Flywheel: the Meaning of Life singer says a thyroid condition — and consequent changing of her eating habits — have amounted to weight loss.

In a new interview with Extra, Clarkson says reading The Plant Paradox by cardiac surgeon Steven R. Gundry totally changed her life.

“I literally read this book, and I did it for this autoimmune disease that I had and I had a thyroid issue, and now all my levels are back up. I’m not on medicine anymore because of this book,” she explains. “It’s basically about how we cook our food, non-GMO, no pesticides, eating really organic.”

“I’m not working out! I think people think I’m working out and I’m like, ‘Don’t think I’m going to come play some sport!’” she adds. “Literally, I haven’t worked out at all!”

Clarkson had previously told Entertainment Tonight that she never meant to lose weight, and that her changing body was more accident than intent.

“I have to shout out my whole glam squad,” Clarkson joked of her sleek physique after The Voice finale in May. “I literally hired Harry Potter and SPANX; it’s all like a sausage.”

“I feel like it’s like the mom makeover on the TODAY show. I walk in and then I walk out and I’m like, ‘Damn!’” she added. “I would love to take any credit for anything that’s happening with the glam squad, but my team is insane.”

Kelly Clarkson Stuns on the Billboard Music Awards Red Carpet