Brown and beige adipose tissues contain thermogenic fat cells that can be activated by β3-adrenergic receptor agonists. In rodents, such drugs both diminish obesity and improve glucose homeostasis. In this issue of the JCI, O’Mara et al. and Finlin and Memetimin et al. report that chronic administration of the approved β3 agonist mirabegron to human subjects was without effect on body weight or fat mass, but improved several measures of glucose homeostasis. Though the mechanisms mediating these metabolic effects are uncertain, the data suggest that β3 agonists could have therapeutic utility in disorders of glucose homeostasis.