To determine whether there are sex differences in stimulated lipolysis in aging mice, we used the ADRB3 agonist; CL-316, 243 (CL) in old male and female C57Bl6/j mice placed on HFD at 10 months of age for 16- week (60% HFD) to induce obesity over the same length of time as our young mice experiments [24, 25, 27]. The gene discussed is ADRB3; the disease is obesity due to melanocortin 4 receptor deficiency.