Klinefelter syndrome is a disorder of chromosomes in which common karyotype is (47XXY). Hypogonadism, gynecomastia and azoospermia could be detected in this syndrome. Decreased basal metabolic rate and interest in activities, loss of muscle mass, weight gain, the deficiency of sex hormone and mood changes cause obesity which cause morb obese in this case.

A 34-year-old morbid obese (BMI = 60.40) male was come to the Laporoscopy research center of Iran University of Medical science at 26 January 2016. He was diagnosed as Klinefelter syndrome by genetic testing (47XXY karyotype). He reported suffering from knee cellulitis, headache, low back pain and varices. His nutrition habits was fast eating, Sweet eating and Snack eating. The beginning of his obesity was in his childhood. The best treatment for his obesity and its side-effects is altering in his life style, low calorie diet. Finally, if these methodes fail to lose weigth, bariatric surgery is suggested.

In morbid obese patients apporopriate diet, change in calorie intake and life style should be considered as a first line of treatment and finally, surgery may be an option to treat obesity. These two methodes can often help reduce the risk of other diseases (e.g., diabetes, heart disease, and sleep apnea) that are associated with severe obesity.