Diet‐induced obese mice (insulin‐resistant) were treated with N‐acetylcysteine (NAC, 50 mg/kg/day for 15 days). The effects on insulin resistance, fasting glycemia, oxidative stress (measured by DCF oxidation, CAT activity, and GSH levels), and molecular markers (NFκB, PTP1B, JNK phosphorylation, IRS, Akt, and IRS/PI3k association) were assessed post‐treatment. Biochemical and molecular analyses were conducted on tissues from euthanized mice. The gene discussed is PTPN1; the disease is Insulin resistance.