The Influence of Reducing Diets on Changes in Thyroid Parameters in Women Suffering from Obesity and Hashimoto's Disease.

The short version

This randomized study of 100 women explored whether an elimination diet tailored to blood-test food sensitivities works better than a standard weight-loss diet for women who have both obesity and Hashimoto's disease, an autoimmune condition in which the immune system attacks the thyroid gland. Hashimoto's disease is among the most common hormonal causes of obesity, and losing weight is often difficult for people who have it. Participants were recruited at an outpatient obesity clinic in Poland and all kept taking their thyroid hormone medicine (L-thyroxine), selenium and zinc. The researchers measured body fat and key thyroid markers over six months, including TSH, the pituitary hormone that rises when the thyroid underperforms. Women aged 18 to 65 with a BMI above 30 were randomly assigned to one of two groups of 50. Every woman had a blood test for IgG antibodies to foods. Group A followed menus of 1400 to 1600 calories a day that left out the foods flagged by their own results, while group B followed menus with the same calories and nutrient balance but no foods removed. A dietitian prepared new menus each month, and visits at baseline, three months and six months recorded body composition and blood tests. Both groups lost weight and improved, but group A improved more. BMI fell significantly more in group A (p = 0.002), and body fat dropped by 9.72% compared with 7.19% in group B (p = 0.026). TSH fell by 48.03% in group A versus 24.54% in group B (p < 0.001), roughly twice the drop, while fT3 and fT4, the free thyroid hormones measured in the blood, rose more in group A (both p < 0.001). Antibodies against the thyroid fell by an average of 269.33 IU/mL (anti-TPO) in group A versus 95.59 IU/mL in group B, and a second antibody, anti-TG, fell by 111.45 versus 60.8 IU/mL. Greater weight loss tracked with greater TSH reduction (r = 0.500). The authors suggest that the elimination diet may work through anti-inflammatory effects, which they say needs testing in larger groups. Limitations include no reported blinding, small differences in starting antibody and hormone levels between groups, and selenium and zinc given to everyone, so their effect cannot be separated. The study did not include a group that took the food-sensitivity test without changing diet. The results apply to women with obesity and Hashimoto's disease who take L-thyroxine.

Key findings

• In this six-month study, 100 women with obesity and Hashimoto's disease (an autoimmune thyroid condition) all took L-thyroxine, selenium and zinc and were randomly assigned to a calorie-reduced diet with foods removed according to an IgG food-sensitivity blood test (group A) or the same diet without removals (group B).
• Both groups lost weight, but BMI fell more in group A (p = 0.002) and body fat fell by 9.72% versus 7.19% in group B (p = 0.026).
• TSH (thyroid stimulating hormone, which rises when the thyroid underperforms) fell 48.03% in group A versus 24.54% in group B (p < 0.001), and fT3 and fT4 (thyroid hormones) rose more in group A (p < 0.001).
• Thyroid antibodies fell more in group A: anti-TPO by 269.33 versus 95.59 IU/mL (p = 0.001) and anti-TG by 111.45 versus 60.8 IU/mL (p = 0.048); greater weight loss tracked with greater TSH reduction (r = 0.500).
• Interpretation is limited because blinding was not reported, baseline fT3 and anti-TPO differed between groups, both arms also took selenium and zinc, and there was no test-only comparison group.

Common questions