Assessing Metabolic Health With Stable Isotope Tracer Techniques in Adults With Obesity

1. Enrollment, Informed Consent, and Screening Questionnaires (Virtual): Prior to study enrollment, participants will be asked to read a digital copy of an informed consent document provided using the e-Consent framework through the Research Electronic Data Capture (REDCap) system. Should participants have any questions about the study after reading the document, they will be encouraged to contact the research team prior to providing informed consent. Upon provision of informed consent, participants will receive an email with questionnaires designed to assess eligibility for the study through REDCap. Specifically, participants will be asked to complete a health and medical history questionnaire, physical activity readiness questionnaire (PARQ), International Physical Activity Questionnaire Long Form (IPAQ), and Godin-Shephard Leisure-Time Physical Activity Questionnaire (LTPAQ). Information from the medical history questionnaire, PARQ, and LTPAQ will be used to assess exclusion criteria and the IPAQ be used to assess baseline habitual activity level. Upon completion of these questionnaires, the research team will review responses and determine eligibility. Should Participants be eligible, researchers will work with the participant to schedule subsequent visits
2. Preliminary Testing (Visit 1): Participants will arrive for the preliminary testing session after an overnight fast.

Urine samples: 30mL of urine at time points -30 min, 0 min, 240 min, 300 min, and 360 min. Briefly, participants will be provided with a urine collection cup, alcohol wipes, and gloves and asked to fill the cup about 3/4 of they way.

Blood Collection: ~88 mL will be collected during the trial.

Breath Collection: At -30 minutes, 0 minutes, 120 minutes, 240 minutes, 300 minutes, 360 minutes, we will measure the air exhaled. To do this, participants breathe normally through a hose. Immediately after, they will exhale into a separate mouthpiece attached to a plastic bag.

Muscle Collection: A total of 2 muscle biopsies will be collected during the trial. The biopsy procedure involves removal of a small piece of muscle tissue using a sterile hollow needle (Bergström needle) and will be performed by Dr. Nicholas Burd under the auspices of Dr. Jared Willard, MD. Participants will rest on a bed and the area for the biopsy will be shaved, if required. Subsequently, the area will be sterilized using 4% chlorhexidine gluconate before 5 mL of local anesthetic (2% Xylocaine with 1:100,000 epinephrine) is injected subcutaneously with special care to avoid infiltrating the muscle. Once the anesthetic is active, a small incision will be made in the skin in order to create an opening through which to put the biopsy needle for tissue collection. Dr. Burd will quickly cut of a small piece of muscle. the subjects may feel a sensation of deep pressure in their leg. A sterile disposable drape will be placed under the participant's thigh and sterile gloves will be used for all biopsy procedures.