Body Composition and Eating Habits in Newly Diagnosed Graves' Disease Patients Compared with Euthyroid Controls

Objectives: Graves' disease (GD) is the most common cause of hyperthyroidism and is associated with marked changes in body weight and body composition. Although weight loss is frequently reported, the extent and clinical relevance of body composition alterations, as well as their relationship with thyroid function, remain unclear. This study aimed to evaluate body composition and eating habits in patients with newly diagnosed hyperthyroid GD according to pre-morbid weight variation, and to compare these findings with those of matched euthyroid controls. Methods: Forty-four consecutive GD patients were enrolled and stratified based on the presence or absence of pre-morbid weight loss. Anthropometric measurements, thyroid function tests, thyroid volume, dietary habits (PREDIMED score, macronutrient intake and total daily caloric intake) and body composition assessed by bioelectrical impedance analysis (BIA) were collected. Standardized phase angle (SPA) and body cell mass index (BCMI) were calculated as nutritional indices. Body composition parameters and dietary adherence were compared with those of 44 age-, sex- and BMI-matched euthyroid controls. Results: Most GD patients (70.3%) reported weight loss before diagnosis; however, the magnitude of weight change did not correlate with the biochemical severity of thyrotoxicosis. Patients without weight loss showed higher fat mass percentage and higher caloric intake than those who lost weight. SPA was significantly associated with FT3, FT4 and TRAb levels, independently of age, sex, BMI and fat mass. Compared with controls, GD patients exhibited lower phase angle and SPA, higher extracellular water percentage and reduced BCMI, whereas fat mass and adherence to the Mediterranean diet were similar. Conclusions: Hyperthyroid GD patients display increased extracellular water and reduced body cell mass. SPA is inversely associated with GD severity and represents a valuable clinical tool for assessing nutritional status in thyrotoxic patients. Pre-morbid weight changes are not proportional to disease severity and may instead reflect increased caloric intake.