The neuropeptide kisspeptin regulates reproduction by stimulating gonadotropin-releasing hormone (GnRH) neurons via the kisspeptin receptor KISS1R. In addition to GnRH neurons, KISS1R is expressed in other brain areas and peripheral tissues, which suggests that kisspeptin has additional functions beyond reproduction. Here, we studied the energetic and metabolic phenotype in mice lacking kisspeptin signaling (Kiss1r KO mice). Compared with WT littermates, adult Kiss1r KO females displayed dramatically higher BW, leptin levels, and adiposity, along with strikingly impaired glucose tolerance. Conversely, male Kiss1r KO mice had normal BW and glucose regulation. Surprisingly, despite their obesity, Kiss1r KO females ate less than WT females; however, Kiss1r KO females displayed markedly reduced locomotor activity, respiratory rate, and energy expenditure, which were not due to impaired thyroid hormone secretion. The BW and metabolic phenotype in Kiss1r KO females was not solely reflective of absent gonadal estrogen, as chronically ovariectomized Kiss1r KO females developed obesity, hyperleptinemia, reduced metabolism, and glucose intolerance compared with ovariectomized WT females. Our findings demonstrate that in addition to reproduction, kisspeptin signaling influences BW, energy expenditure, and glucose homeostasis in a sexually dimorphic and partially sex steroid–independent manner; therefore, alterations in kisspeptin signaling might contribute, directly or indirectly, to some facets of human obesity, diabetes, or metabolic dysfunction.