Some individuals are more prone to weight gain whilst others remain resistant following consumption of a high-energy diet (HED). The exact mechanism(s) underpinning this difference are not fully understood, particularly whether peripheral and/or central impairments are involved. We have generated a model of diet-induced obesity in female isogenic C57Bl6/J (B6) mice in which those that gained 25% more weight following 6 weeks of a HED were classified as DIO and those that had similar weight gain to the chow-fed B6 mice classified as resistant (DR). Our aim was to determine what physiological, biochemical and genetic changes occur that differentiate susceptibility and resistance in these mice. The increase in body weight in the DIO mice was accompanied by significant increases across all three fat depots measured (subcutaneous, infra-renal and gonadal). DIO mice ate 29% more food than the DR mice translating to an extra 30% of calories consumed, yet energy expenditure (activity and resting) was unchanged. Circulating gut hormone profiling showed increased plasma insulin, leptin, adiponectin, GIP and GLP-1 in the DIO mice compared to the DR and chow-fed B6 mice. When arcuate nuclei neuropeptide mRNA expression levels were measured, DIO mice showed significantly elevated POMC expression compared to the DR mice (40%) and chow-fed mice (76%), but no changes in NPY, AgRP or SOCS3. Leptin mRNA expression in the infra-renal fat depot was trending higher in the DIO mice compared to the chow-fed B6 mice (p=0.06) but was markedly suppressed compared to the DR mice (61%, p<0.05). These results suggest that susceptibility to weight gain 6 weeks following a HED in genetically similar mice may involve impairments at both the peripheral and central levels whilst resistance may involve peripheral only effects. Therefore in response to energy excess, the predisposition to weight gain and resistance may be driven by alternate mechanisms.