The Oxylet System monitors respiratory metabolism in rodents. Utilizing an indirect calorimetry system, it easily monitors CO2 production, O2 consumption, and respiratory ratio. It can be scaled up to accommodate up to 32 animals simultaneously. As each animal chamber has its independent flow meter, one system can accommodate multiple species at the same time. The Oxylet is useful for studies of obesity, diabetes, athletic exercise training, and other respiratory-challenging conditions.