Oxygen consumption by Zucker obese rats, obese yellow mice, and obese hyperglycemic mice with body protein used for metabolic mass.

Oxygen consumption was determined in three varieties of genetically-obese rodents and their lean littermates; the Zucker obese rat (fa/fa), the obese hyperglycemic mouse (ob/ob), and the yellow obese mouse (Ay/a). Values were expressed with both live body weight and total body protein as the unit of metabolic body size. When oxygen consumptions were expressed on the basis of live body weight, all three obese varieties exhibited lower values than their age-matched non-obese littermates. When values of oxygen consumption were expressed with total body protein as the unit of metabolic size, only the ob/ob mice had lower oxygen consumptions than their non-ob/ob littermates. The fa/fa rats and the Ay/a mice had similar values of oxygen consumption as their non-obese controls. Much better correlations between whole-animal resting oxygen consumption, reported values of maintenance energy requirements, and tissue oxygen consumption are obtained when body protein content rather than live body weight is used as the unit of metabolic mass.