Clinical Research Directory

* INCLUSION CRITERIA: In order to be eligible to participate in this study, an individual must meet all of the following criteria: * Aged 18 to 55 years. * Able to provide informed consent. * Willing and able to stay in the whole-room indirect calorimetry suite on 6 occasions. * Willing to reside on the metabolic unit in the Clinical Center for 2 stays of 11 consecutive days over the course of 5 weeks. * Willing to allow samples and data to be stored and shared for future research. EXCLUSION CRITERIA: An individual who meets any of the following criteria will be excluded from participation in this study: * Current infection with HIV or hepatitis A, B, or C. * Body mass index (BMI) \<18.5 kg/m\^2 or \>30.0 kg/m\^2. * Weight change \>5% in the past 6 months or a trained athlete. * History of or current cardiovascular disease such as congestive heart failure, heart block, or clinically relevant abnormal ECG as determined by investigators. * History of or current liver disease or alanine transaminase serum level \>2x upper limit of normal. * History of or current kidney disease or renal insufficiency, or estimated creatinine clearance \<=50 mL/min (Modification of Diet in Renal Disease equation). * Current cancer or history of cancer within 5 years of screening, with the exception of squamous cell carcinoma or basal cell carcinoma that is localized and does not require systemic therapy. * History of bariatric surgery. * Diabetes mellitus. * Fasting serum glucose \>126 mg/dL. * History of or current hypo- or hyper-thyroid or abnormal TSH, except minor deviations deemed to be of no clinical significance by the investigator. * History of or current asthma or chronic obstructive pulmonary disease. * History of or current glaucoma. * Psychological conditions by self-report, such as (but not limited to) claustrophobia, clinical depression, bipolar disorders, that would be incompatible with safe and successful participation in this study. * Pregnancy or within 1 year post-partum. * Experiences irregular menstrual cycles. * Breastfeeding. * Blood pressure \>140/90 mm Hg or current antihypertensive therapy. * Anemia, defined as hemoglobin \<13 g/dL (males) or \<12 g/dL (females). * History of illicit drug, opioid, or alcohol abuse within the last 5 years; current use of illicit drugs or opioids (by history) or excessive alcohol (CAGE assessment score \>=2). * Current use of medications/dietary supplements/alternative therapies known to alter energy metabolism. * Current use of the following prescription or over-the-counter medications and supplements: * Carbamazepine * Oxcarbazepine * Phenobarbital * Phenytoin * Primidone * Rifabutin * Rifampin * Rifapentine * St. John's wort (Hypericum perforatum) * Cation-containing antacids or laxatives * Sucralfate * Buffered medications * Oral calcium, iron, magnesium, or zinc supplements, including multivitamins containing these polyvalent cations * Dalfampridine * Metformin * Dofetilide * Thyroid medications * Corticosteroids * Weight loss medications, including prescription drugs (eg, semaglutide and tirzepatide) and over-the-counter diet pills * Hormone medications for any indication * Use of tenofovir alafenamide (Descovy) or tenofovir disoproxil fumerate (Truvada) for the purpose of HIV PrEP within the past 6 months. * Any history of exposure to cabotegravir (eg, as HIV PrEP or as a participant in research study for this drug). * Current use of nonprescriptive medications that may have interactions with study drugs as determined by the investigators. * History of adverse or allergic reactions to the study drugs. * Daily caffeine intake \>500 mg (about 4 cups of coffee) * Current smoker or user of tobacco products. * Participants with dietary allergies, intolerances, or eating patterns that would preclude them from consuming controlled metabolic meals. * Any condition that, in the opinion of the investigator, contraindicates participation in this study.