For obese type 2 diabetes patients, weight reduction is one of the most important measures but fails in most cases. Testosterone deficiency can be the reason for such failure. This case presents a 57-year-old man who was referred to a urologist due to benign prostatic hyperplasia and erectile dysfunction. He had type 2 diabetes, was overweight, and had hypertension and dyslipidemia. The blood test revealed testosterone deficiency. Under testosterone therapy, the patient lost 10 kg; cardiometabolic parameters returned to normal and lower urinary tract symptoms disappeared; complete remission of diabetes was recorded. Overweight and obese patients with type 2 diabetes should be tested for hypogonadism and testosterone therapy, if indicated, be considered. These patients can considerably benefit from testosterone therapy in terms of sustainable weight loss and a clinically significant reduction of cardiometabolic risk factors including complete remission of diabetes.