Everything You Need to Know About the Diet That Led to Kelly Clarkson's 37-Lb. Weight Loss

Kelly Clarkson has now lost 37 lbs., and she says the credit goes to her new clean eating diet.

The singer, 36, changed up her eating habits after dealing with a thyroid issue, and decided to follow the regimen prescribed in the book The Plant Paradox, by Dr. Steven R. Gundry.

“I did it for this autoimmune disease that I had and I had a thyroid issue,” Clarkson explained. A source adds to PEOPLE that “weight loss wasn’t the goal,” for the mom of two. “This was an overall health approach.”

The Plant Paradox plan takes a fairly restrictive approach to eating, and eliminates foods high in lectins, a protein that is “present in most foods to some degree, but highest in foods like beans and grains,” Marisa Moore, an Atlanta-based registered dietitian, tells PEOPLE.

The program has dieters cut out most starches, from brown rice to potatoes; vegetables that are thought to cause inflammation, like tomatoes, peppers, chickpeas and more; all fruit, except for in-season berries; some forms of dairy like Greek yogurt and cottage cheese; and more.

But Moore says the diet is more of a “fad.”

“Many of the claims regarding lectins and how they affect the body seem to be largely overblown without much human research to support them,” she says. “Soaking and cooking destroys most lectins. and you can also ferment and sprout foods to help reduce lectin presence. (And I don’t know anyone that eats raw quinoa or kidney beans anyway.)”

Dawn Jackson Blatner, a Chicago-based dietician and member of PEOPLE’s Health Squad, agrees, adding that the whole grains and legumes that this program cuts out are typically part of the healthiest diets in the world, and not something that causes weight gain.

She agrees, though, that The Plant Paradox is an effective health and weight-loss tool, mostly because it promotes healthier eating overall.

“People will see success with this diet because they are removing so many foods, are forced to do more mindful food choices and will have to prep more whole foods at home,” Blatner tells PEOPLE. “All things that lead to better health, habits and weight loss.”

She adds, “It’s not the absence of lectins that’s magical, it’s that people following this plan aren’t eating pizza, baked goods and other junk food, and they’re swapping those things for more real food such as veggies, healthy fats and quality animal proteins. When you eat a variety of wholesome foods — with and without lectins — you will get results.”