INS and obesity due to melanocortin 4 receptor deficiency: There are several reasons for increased free fatty acids in obesity: (1) enlarged adipose tissue resistant to the antilipolytic effect of insulin; (2) increased liver fatty acid de novo synthesis (Jacome-Sosa and Parks, 2014; Björnson et al., 2016; Xiao et al., 2016); (3) increased uptake of triglyceride-rich lipoproteins by the liver (Yu and Ginsberg, 2005; Dash et al., 2015; Björnson et al., 2016; Xiao et al., 2016).