The ogt gene encodes O-linked N-acetylglucosamine transferase (O-GlcNAc transferase [OGT]) that catalyzes the transfer of β-N-acetylglucosamine (GlcNAc) from the uridine-diphosphate-GlcNAc to the hydroxyl group of serine or threonine residues of nucleocytoplasmic proteins. This process is a common protein posttranslational modification, called protein O-GlcNAcylation, which is a known intracellular sensor of glucose metabolism and plays an important role in regulating cellular signaling, transcription, and metabolism. However, little is known about the function of OGT in the brain. Here, we report that the CaMKIIα promoter-dependent neuronal knockout (KO) of OGT in adult mice led to short-term overeating, body weight gain, and peripheral insulin resistance. These phenotype changes were accompanied by marked elevation of serum insulin and leptin levels and neuronal cell death, including the loss of leptin receptor-expressing neurons, in the hypothalamus. The neuronal OGT KO exacerbated obesity and insulin resistance induced by high-fat diet. Surprisingly, the peripheral insulin resistance induced by neuronal OGT KO was reversed at its own 2-3 months after OGT KO, and the mice even showed increased insulin sensitivity several months later. These findings reveal an important role of neuronal OGT in the regulation of feeding behavior, body weight, and peripheral insulin sensitivity.