Studying Brown Fat's Role in Metabolism

Inclusion criteria: 1\. Healthy participants between age 18 and 75 years undergoing planned clinically indicated procedure at BIDMC. Exclusion Criteria: 1. Body mass index (BMI) greater than or equal to 40 kg/m2 2. History of any local or systemic infectious disease with fever or requiring antibiotic within four weeks of drug administration; 3. Diabetes, either previously diagnosed or hemoglobin A1c greater than or equal to 6.5% 4. Use of oral or parenteral corticosteroids (epidural permitted) or other medication known to cause insulin resistance in the previous 6 weeks. 5. Willingness to provide informed consent and follow study procedures, including attending scheduled visits. 6. Chronic kidney disease stage 4 or 5 (including end-stage renal disease); 7. Hepatic disease, including serum alanine aminotransferase (ALT) or aspartate transaminase (AST) greater than or equal to 3 times the upper limit of normal; hepatic synthetic insufficiency as defined as serum albumin \< 3.0 g/dL; or serum bilirubin \> 2.0; 8. Active malignancy (except squamous or basal cell carcinoma of skin) 9. Bleeding disorder, treatment with anticoagulants (if not discontinued prior to surgery), or platelet count \<50,000; 10. Current addiction to alcohol or substances of abuse; 11. Mental incapacity, unwillingness or language barriers precluding adequate understanding or cooperation; 12. Use of an investigational drug within 30 days prior to screening. 13. There will be no involvement of special vulnerable populations such as fetuses, neonates, pregnant women, children, prisoners, institutionalized or incarcerated individuals, or others who may be considered vulnerable populations. 14. Because the goal is to study adult human brown adipose tissue, children are not eligible to participate.