Her identical twin sister has Hashimoto’s disease, in which the body’s immune system attacks the thyroid gland, along with celiac disease. Flanigan and her sister both follow the diet. As clients go through diet phases, Flanigan monitors their symptoms, and working with their doctors, she tracks results of medical tests to detect inflammation. Of clients’ doctors, she says, about “25 percent are open and agreeable” to the diet, while the rest are resistant.