Dietary Macronutrients and Metabolic Markers

Effects of a 12-Week Ketogenic Diet on Thyroid Function and Glucose-Insulin Metabolism in Premenopausal Women Across Different Adiposity Categories

This prospective 12-week dietary intervention study evaluated the effects of a ketogenic diet on thyroid function and glucose-insulin metabolism in premenopausal women aged 30-50 years across different adiposity categories. Participants followed an individualized low-carbohydrate ketogenic diet designed to induce and maintain nutritional ketosis. Thyroid-related outcomes included thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4). Glucose-insulin metabolism was assessed using fasting glucose, fasting insulin, glycated hemoglobin (HbA1c), and the homeostatic model assessment of insulin resistance (HOMA-IR). Changes in body mass and anthropometric parameters were also evaluated. Outcomes were assessed before and after the 12-week intervention and compared according to baseline BMI categories.

Inclusion Criteria:

• Premenopausal status
• No use of a specific diet, calorie-restricted diet, or food-elimination regimen during the preceding 12 months
• Willingness to follow the prescribed ketogenic diet for 12 weeks
• Provision of written informed consent

Exclusion Criteria:

• Postmenopausal status
• Pregnancy or breastfeeding
• Previously diagnosed thyroid disease
• Thyroid hormone replacement therapy
• Use of antithyroid medication
• Use of other pharmacological treatments known to substantially affect thyroid function
• Use of dietary supplements known to substantially affect glucose or lipid metabolism before enrollment
• Use of pharmacological treatment for insulin resistance
• Use of pharmacological treatment for dyslipidemia