Validating a Novel Approach to Assess Metabolic Flexibility in a Respiratory Chamber

Participants will spend 13 hours (overnight) in a metabolic chamber where they will be fed a single high-fat supper meal. Energy expenditure, respiratory exchange ratio (RER), and 12-h oxidation of CHO, fat, and protein will be calculated and used to determine metabolic flexibility, i.e. change in RER from baseline.

Metabolic flexibility with be assessed during a 2-step hyperinsulinemic-euglycemic clamp procedure. The clamp will be performed for four hours, two hours at an insulin dose of 10 mU/m\^2/min and two hours at an insulin dose of 80 mU/m\^2/min. Resting metabolic rate will be determined via hood indirect calorimetry at baseline, before insulin onset, and during the final 30 min of each step of the clamp. Metabolic flexibility will be determined by comparing the resting metabolic rate during baseline and during the final 30 min of each step of the clamp.