Inclusion Criteria:
1. Group 1 cohort are male or female participants between 18 and 30 years old
2. Group 2 cohort are male or female participants ≥ 65 years old
3. Body mass index (BMI) ≤ 40 kg/m2
4. Weight stable (±5 kg) for the last 3 months prior to the Screening visit
5. Sedentary (\<20 min of activity, 3x/week).
6. Able to speak and understand written and spoken English
7. Willing and able to comply with scheduled visits, laboratory tests, and other study procedures
8. Participant has voluntarily signed and dated an informed consent form, approved by an Institutional Review Board/Independent Ethics Committee, and provided Health Insurance Portability and Accountability Act authorization (HIPAA) or other privacy authorization prior to any participation in study
Exclusion Criteria:
1. Diagnosis of type 1 diabetes mellitus
2. Diagnosis of type 2 diabetes mellitus (HbA1C ≥ 6.5)
3. Insulin use and use of any other medications for diabetes.
4. Use of metformin for polycystic ovarian disease
5. Untreated or poorly controlled hypertension (SBP \> 160, DBP \> 100)
6. Participants are actively pursuing weight loss and/or lifestyle changes
7. Participants have a sensitivity or allergy to lidocaine
8. Drug or alcohol abuse (\> 3 drinks per day) within the last 5 years
9. Any unstable medical condition (i.e., coronary heart disease, stroke, chronic renal failure \[serum creatinine should not exceed 1.5-fold the upper laboratory norm and estimated eGFR should not be lower than 60 mL/min/1.73 m2 at screening\], chronic hepatic disease, severe pulmonary disease, bleeding disorders, autoimmune disease, active rheumatoid arthritis or other inflammatory rheumatic disorder, or gastrointestinal disease requiring medication)
10. Participants currently taking anti-inflammatory medications within 2 days prior to biopsy or antiplatelet medications within 7 days prior to biopsy, that cannot be safely stopped for study procedures
11. Participants who have a TSH \>10 µIU/ml or less than 0.4 µIU/ml
12. Triglycerides \>500
13. Pregnant or nursing females or females less than 9 months postpartum.
14. For females only, any new onset (\< 3 months on a stable regime) use of oral contraceptives (with the exception of hormone replacement therapy)
15. Tobacco or nicotine containing product use within the past 3 months
16. Major surgery within 4 weeks prior to the Screening Visit
17. Anemia (hemoglobin \<11 g/dl in men, \<10 g/dl in women) at Screening
18. Participation in studies involving investigational drug(s) within 30 days prior to the Screening Visit
19. Known history of Human Immunodeficiency Virus (HIV), chronic, contagious, infectious disease, such as active tuberculosis, Hepatitis B or C.
20. Any malignancy not considered cured, except basal cell carcinoma and squamous cell carcinoma of the skin (a participant is considered cured if there has been no evidence of cancer recurrence in the previous 5 years)
21. Presence of any condition that, in the opinion of the Investigator, compromises participant safety or data integrity or the participant's ability to complete study visits
