A great number of studies indicated that there was a negative correlation between ghrelin and IR in obesity (Ikezaki et al., 2002; Pedrosa et al., 2011; Wadden et al., 2012; Al Qarni et al., 2017), while some studies obtained different results: In the study of Stepien et al., the ghrelin was negative with IR in the obesity plus insulin sensitivity group while positive with IR in the obesity plus insulin resistance group (Stepien et al., 2011). The gene discussed is INS; the disease is obesity due to melanocortin 4 receptor deficiency.