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.
This prospective, single-group, 12-week dietary intervention study investigated the effects of a ketogenic diet on thyroid function and glucose-insulin metabolism in premenopausal women aged 30-50 years. Participants were classified according to baseline BMI into normal-weight, overweight, and obesity categories for analytical purposes. All participants received the same ketogenic dietary intervention; BMI categories did not represent separate intervention arms. The ketogenic diet was individually prescribed and characterized by very low carbohydrate intake, moderate protein intake, and a high proportion of dietary fat. Participants received individualized dietary plans and nutritional counseling throughout the intervention. Nutritional ketosis was monitored during the study. Assessments were performed at baseline and after 12 weeks. Thyroid function was evaluated using serum TSH, FT3, and FT4 concentrations. Glucose-insulin metabolism was assessed using fasting glucose, fasting insulin, HbA1c, and HOMA-IR. Body mass and anthropometric measurements were also obtained to evaluate changes in adiposity-related parameters. A total of 150 women were screened for eligibility, 120 entered the intervention, and 100 completed the 12-week study. The study was conducted at the Jerzy Kukuczka Academy of Physical Education in Katowice, Poland. The primary objective was to determine whether the metabolic and thyroid responses to a ketogenic diet differed according to baseline adiposity.
Study Type
INTERVENTIONAL
Allocation
NA
Purpose
BASIC_SCIENCE
Masking
NONE
Enrollment
120
Participants will follow an individualized low-carbohydrate ketogenic diet for 12 weeks. The diet will provide approximately 8-10% of total energy from carbohydrates, 65-75% from fat, and 20-25% from protein. Individual energy requirements will be estimated and dietary plans will be adjusted accordingly. Participants will receive nutritional counseling and individualized meal plans to support adherence to the prescribed diet. Nutritional ketosis will be monitored throughout the intervention by measuring blood β-hydroxybutyrate (BHB) concentrations.
Institute of Sport Sciences, Jerzy Kukuczka Academy of Physical Education in Katowice
Katowice, Poland
Change in Thyroid-Stimulating Hormone (TSH)
Serum thyroid-stimulating hormone (TSH) concentration will be assessed to evaluate changes in thyroid function following the 12-week ketogenic diet intervention.Unit- µIU/mL
Time frame: Baseline and 12 week
Change in Fasting Insulin
Fasting serum insulin concentration will be assessed to evaluate changes in insulin metabolism following the 12-week ketogenic diet intervention. Unit: µIU/mL
Time frame: Baseline and 12 weeks
Change in Fasting Glucose
Fasting blood glucose concentration will be assessed at baseline and after the 12-week ketogenic diet intervention to evaluate changes in glucose metabolism. Unit: mg/dL
Time frame: Baseline and 12 weeks
Change in Free Thyroxine (FT4)
Serum free thyroxine (FT4) concentration will be assessed to evaluate thyroid hormone responses to the 12-week ketogenic diet intervention.Unit: ng/dL
Time frame: Baseline and 12 weeks
Change in Free Triiodothyronine (FT3)
Serum free triiodothyronine (FT3) concentration will be assessed to evaluate thyroid hormone responses to the 12-week ketogenic diet intervention.Unit: pg/mL
Time frame: Baseline and 12 weeks
Change in Glycated Hemoglobin (HbA1c)
HbA1c will be assessed to evaluate changes in glycemic control following the 12-week ketogenic diet intervention. Unit: %
Time frame: Baseline and 12 weeks
Change in HOMA-IR
Insulin resistance will be estimated using the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR), calculated from fasting glucose and fasting insulin concentrations. Unit: dimensionless index
Time frame: Baseline and 12 weeks
Change in Beta-Hydroxybutyrate (BHB)
Blood beta-hydroxybutyrate (BHB) concentration will be assessed as a biochemical marker of ketogenic exposure and to confirm nutritional ketosis. Unit: mmol/L
Time frame: Baseline and 12 weeks
Change in Hip Circumference
Hip circumference will be measured using a non-elastic anthropometric measuring tape at the maximal circumference over the hip and buttock region. Changes from baseline to the end of the 12-week ketogenic diet intervention will be evaluated. Unit: cm
Time frame: Baseline and 12 weeks
Change in Thigh Circumference
Thigh circumference will be measured using a non-elastic anthropometric measuring tape at a standardized anatomical site on the thigh. The same measurement site will be used at baseline and after the intervention. Changes from baseline to the end of the 12-week ketogenic diet intervention will be evaluated. Unit: cm
Time frame: Baseline and 12 weeks
Change in Body Mass Index (BMI)
Body mass index (BMI) will be calculated as body mass in kilograms divided by height in meters squared (kg/m²). Body mass will be measured under standardized fasting conditions using the InBody 220 analyzer, and height will be measured using standard anthropometric procedures. Changes in BMI from baseline to the end of the 12-week ketogenic diet intervention will be evaluated. Unit: kg/m²
Time frame: Baseline and 12 weeks
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