Oxidative phosphorylation (OXPHOS) is associated with anti-inflammatory macrophages, whereas enhanced glycolysis has been associated with pro-inflammatory macrophages. In Immunity, Wculek et al. find that OXPHOS also distinguishes different tissue-resident macrophages (TMFs) at steady state. OXPHOS was identified as the biological pathway that was the most transcriptionally different among TMFs from 11 different tissues. Conditional knockout of Tfam (which encodes a mitochondrial transcription factor) to impair OXPHOS in all macrophages resulted in increased apoptosis and reduced proliferation of specific populations of TMFs, including alveolar macrophages (AMs). The function of AMs is primarily the removal of lipid-rich surfactant found in the lungs; when OXPHOS was disrupted, there was deregulated lipid handling that resulted in reduced proliferation and increased apoptosis. Other TMFs with high lipid-processing activities were similarly affected. TMFs from white adipose tissue are quiescent in lean mice and were unaffected by impaired OXPHOS, but when mice were maintained on a high-fat diet, disruption of OXPHOS resulted in less weight gain. Thus, OXPHOS is required for the maintenance of macrophage populations with high lipid-handling activity, and interfering with this process may ameliorate obesity.