Stearoyl-CoA desaturase (SCD) is a regulatory enzyme in lipogenesis. The enzyme is constitutively expressed in adipose tissue and is induced in liver in response to fat free, high carbohydrate diet. Several SCD isoforms (SCD1, -2, and -3) exist in the mouse. Mice with a targeted disruption of the SCD1 isoform had reduced body adiposity, increased insulin sensitivity, and resistance to diet-induced weight gain. The protection from obesity involved increased energy expenditure and increased oxygen consumption. SCD1 deficiency shows activation of lipid oxidation in addition to reduced triglyceride synthesis and storage.