De novo lipogenesis (DNL) is a complex yet highly regulated metabolic pathway, and transcription factors such as liver X receptor (LXR), sterol regulatory element-binding protein-1c (SREBP-1c), and carbohydrate response element binding protein (ChREBP) exert significant control over the de novo synthesis of fatty acids. An increase in de novo lipogenesis (DNL) is an important contributor to increased fat mass, while a reduction in lipogenesis may be protective against the development of obesity. In this review, we explore fatty acid synthesis in the context of new insights gleaned from global and tissue-specific gene knockout mouse models of enzymes involved in fatty acid synthesis, namely acetyl-CoA carboxylase, fatty acid synthase, fatty acid elongase 6, and stearoyl-CoA desaturase 1. A disruption in fatty acid synthesis, induced by the deficiency of any one of these enzymes, affects lipid metabolism and in some cases may protect against obesity in a tissue and gene-specific manner, as discussed in detail in this review.