The primary purpose of this protocol is to develop a reliable method to determine BAT mass in young and older adults by magnetic resonance imaging.

Inclusion Criteria:

• Capable of providing informed consent and has voluntarily signed and dated an informed consent form, approved by an Institutional Review Board and provided Health Insurance Portability and Accountability Act authorization (HIPAA) or other privacy authorization prior to any participation in study.
• Adult female or male, 20-40 or 60-80 years of age, inclusive at time of screening.
• BMI ≥19.0 and ≤34.9 kg/m2, inclusive at time of screening.
• Stable weight (No gain/loss of ≥ 10 lbs within 6 months prior to screening).
• Non-smokers as defined by not smoked any tobacco or nicotine-containing products vape pens or vaporizers within 3 months prior to screening.

Exclusion Criteria:

• History of type 1 or type 2 diabetes per self-report at screening visit 1; or Hgb A1c ≥ 6.5% at screening..
• Actively pursuing weight loss and/or lifestyle changes at time of screening.
• Weight > 450 lbs at screening.
• Uncontrolled hypertension (BP >160 mmHg systolic or >100 mmHg diastolic).
• Mini Mental State Exam (MMSE) <21, only applicable for those 60-80 years of age
• Significant cardiovascular event (e.g. myocardial infarction, stroke) ≤ 6 months prior to screening visit; or stated history of congestive heart failure; or evidence of cardiovascular disease assessed during the ECG at screening.
• Current infection (requiring prescription antimicrobial or antiviral medication, or hospitalization), or corticosteroid treatment (with the exception of inhaled or topical steroids) in the last 3 months prior to screening visit.
• Prescription strength anti-inflammatory medication in the 6 weeks prior to screening.
• Surgery requiring >2 days of hospitalization in the last 3 weeks prior to screening visit.
• Active malignancy or autoimmune disease.
• History of chronic, contagious, infectious disease, such as active tuberculosis, Hepatitis B or C, or HIV, per self-report.
• History of uncontrolled severe diarrhea, nausea or vomiting within 3 months of screening.
• Uncontrolled severe (including stage III or above) gastrointestinal absorption-related disorders, within 3 months of screening, such as: obstruction of the gastrointestinal tract, inflammatory bowel disease, short bowel syndrome, gastroesophageal reflux disease, gastroparesis, peptic ulcer disease, celiac disease, intestinal dysmotility, diverticulitis, ischemic colitis.
• History of drug or alcohol abuse (> 3 drinks per day) within the last 5 years.
• Pregnant, lactating or is within 6 weeks postpartum prior to the screening visit.
• Metal implants (pace-maker, aneurysm clips) based on Investigator's judgment at screening.
• Unable to participate in MRI assessments due to physical limitations of equipment tolerances (e.g. MRI bore size) based on Investigator's judgment at screening.
• Unable to tolerate MRI imaging or claustrophobia.
• Urine albumin-to-creatinine ratio (UACR) ≥300 mg/g in a single urine specimen (per National Kidney Foundation guideline) at screening.
• Impaired renal function: estimated glomerular filtration rate (eGFR) ≤ 50 ml/min/1.73m2 determined at screening.
• Significantly impaired liver function in the opinion of the study PI (mild asymptomatic fatty liver is acceptable), or hepatic enzyme tests are ≥2.5 times normal limit at time of screening.
• Total cholesterol level is ˃300 mg/dL at screening.
• Participant has inadequately treated hyperthyroidism (thyroid stimulating hormone [TSH] below normal range) or hypothyroidism (TSH>ULN (upper limit normal) to <10U/mL and symptomatic, or TSH >10 U/mL) at time of screening.

Males and females in the age ranges 20-40 and 60-80 years were recruited. Potential participants were medically screened to determine good health, weight stable (no gain/loss of ≥ 10 lbs in 6 months prior to screening), and without any contraindication to exercise. Approximately equal numbers of men and women will be recruited. Neither race nor ethnicity were exclusions.