Food Intake, Endocrine Factors and Brown Fat

Inclusion Criteria: * • Males and females * Between 18 and 45 years old. * For the lean group: BMI\<25.0 kg/m2 * For the group with overweight/obesity: BMI\>27.5 kg/m2 and a waist circumference of over 94 cm (men) or 80 cm (women). Exclusion Criteria: * • Inability to have PET/CT (claustrophobia, weight \> 150 kg); * Pregnancy and pregnancy-related conditions (postpartum/lactation during the last 12 months, or planning to become pregnant soon); * Major alterations in the menstrual cycle (e.g., amenorrhea); * Use of nicotine-based products; * Hypo- or hyper- thyroidism (medical history, TSH, T3 or T4 levels out of the normal range); * Diabetes mellitus (fasting Hb1Ac \>6.5% or fasting glycaemia\>125 mg/dL) or abnormal oral glucose tolerance test (2h OGTT \> 7.8 mmol/L); * Hypertension (blood pressure \> 160/100 mmHg) or abnormal cardiovascular status (arrhythmia and/or long QTc in ECG, abnormal cardiac murmur, previous history of cardiovascular disease); * Abnormal coagulopathy (e.g., clotting abnormality); * Malignancies, immunological, autoimmune and primary/secondary immunodeficiency disorders (including or not any active treatment). * Virus or bacterial infection (both asymptomatic and symptomatic picture) within the 30 days prior to the study start; * Episode of fever or major surgery, burns and traumas within the month prior to the study start * Chronic infections requiring chronic antibiotic or anti-viral treatment * Whole blood donati…