This study compares the effect of IF in patients with T2D, their first-degree relatives and healthy individuals. Leptin, adiponectin, leptin:adiponectin ratio, HOMA-beta and HbA1c were significantly improved in all groups. Fasting blood glucose and growth hormone levels were improved in control and first-degree relatives. C-peptide, HOMA-IR, HOMA-S and insulin levels were improved in T2D patients and first-degree relatives. CTL comprises healthy control with fasting blood glucose <100 mg/dL. The gene discussed is LEP; the disease is type 2 diabetes mellitus.