The IRS1 gene encodes a protein, insulin receptor substrate 1. It plays a key role in transmitting signals from the insulin and insulin-like growth factor-1 (IGF-1) receptors to intracellular pathways.
If you carry the C-allele, you are predisposed to insulin resistance, impaired insulin sensitivity, hyperinsulinemia and an increased risk for type 2 diabetes. It is important for you for you to look at your genetic variations for PPARG, TCF7L2, and FTO as this could compound or increase your risk for the above.
If you carry the T-allele in this gene, you'll likely have a decreased risk of insulin resistance, T2D and adiposity, and increased insulin sensitivity.