To determine whether the deletion of ELOVL6 could alter the development of insulin resistance, obesity, and fatty livers in response to caloric excess, wild-type and Elovl6−/− mice on the C57BL/6J background were fed a high-fat/high-sucrose diet (45% kcal from fat). The gene discussed is ELOVL6; the disease is obesity due to melanocortin 4 receptor deficiency.