FADS2 and obesity due to melanocortin 4 receptor deficiency: There have been several studies conducted in humans, rats, chicken and cattle investigating the effect of dietary PUFA on mRNA abundance of lipogenic enzymes of carnitine palmitoyl transferase 1 (CPT-1), acetyl-CoA carboxylase (ACC), stearoyl-CoA desaturase (SCD), delta-6 (∆-6) desaturase, delta-5 (∆-5) desaturase, fatty acid synthase in relation to fat metabolism (deposition, energy expenditure, oxidation), obesity, insulin resistance and other autoimmune responses [1,8,11,36,37,38,39].