Thus, the presence of the C allele of the IRS1 gene (rs2943640) may indicate risk of high insulin resistance in type 2 diabetic patients regardless of the presence/absence of comorbid obesity and chronic pancreatitis; in type 2 diabetic patients (carriers of C allele of the IRS1 gene (rs2943640)) with comorbid obesity and chronic pancreatitis, actually, chronic pancreatitis is more important factor in insulin resistance progression. This evidence concerns the gene IRS1 and obesity due to melanocortin 4 receptor deficiency.