1.What is obesity? The basis of obesity and overweight is energy imbalance, that is, energy is not consumed. The lifestyle and pressure of this era shows that it is the root cause of obesity. Global obesity and overweight should be attributed to the intake of excessive fat, sugar, and less activity. 2, obesity how to affect male fertility? Obesity is a complication of a variety of serious chronic diseases, its accompanying diseases including cancer, non-insulin-dependent diabetes, hyperlipidemia, heart disease, hypertension, stroke, psychological depression, sleep apnea syndrome and kidney failure. A large number of studies have shown that obesity is closely associated with infertility and can be considered for study as a complication of obesity. Basically, obesity can affect the male reproductive system and fertility by affecting erectile and semen parameters. Overweight and obese couples have a higher risk of infertility. If both couples are obese, their fertility is at greater risk than if only one couple is obese. This point points to the fact that both partners have an impact on fertility, with the male factor being more dominant. In obese patients, semen parameters are characterized by reduced density, increased malformations, and effects on nuclear chromosome aggregation and sperm motility. Although there is a large body of data suggesting that obesity affects spermatogenesis, not all evidence supports this conclusion. The high prevalence of sperm DNA fragmentation in obese men also suggests that it affects spermatogenesis, which in turn affects sperm density and motility. This leads us to further conclude that obesity not only alters sperm parameters, but also has its roots in influencing spermatogenesis, perhaps through hormonal pathways.