Gastric bypass surgery is among the most preferred surgical interventions in cases of severe obesity. In this type of intervention, a part of the stomach is isolated, the contents of which surround the small intestine and the nutrients in it are not absorbed. As an established method of treating obesity, gastric bypass surgery has received increased attention from both women and men. However, a new study shows that surgery, especially when performed using the method known as Roux-en-Y, carries a serious risk of male infertility. A team from a hospital in Sao Paulo, Brazil, led by scientists from Harvard Medical College, established the alarming data. Their study showed that 57% of men who underwent gastric bypass surgery for obesity developed infertility. The reason for it is the irreversible disorders in the production of sperm, which may occur after the operation. Obesity has long been considered one of the main factors provoking fertility problems in men. The new study shows that some specific methods of combating this problem may also have a negative effect on men’s ability to leave offspring. The study included 80 men divided into 2 groups: obese men who had gastric bypass surgery and obese men who had not yet undergone the procedure. Men without weight problems were used as controls. In all groups, the levels of the most important vitamins and microelements for male fertility, hormone levels and sperm quality were monitored. NEWS_MORE_BOX 4 key patterns have been found in men who have undergone gastric bypass surgery: Increase in estrogen levels; Decreased levels of zinc in the blood; Vitamin D deficiency; Decreased amount of viable sperm in semen; All four factors can lead to sterility in men, and the occurrence of all of them has been associated with the changes that have occurred as a result of gastric bypass surgery. This has led scientists to appeal for greater awareness among obese men before undergoing the procedure in question. It is widely popular among young people suffering from obesity. Its risks must be taken into account in order to avoid early damage to fertility in men of this group.