Men who carry excess body fat are at risk of infertility because they put an inordinate amount of strain on all their major organs, which can interfere with normal sexual activity. However, excess weight can have an even more direct impact on fertility by hampering hormone development, leading to a lower sperm count and increasing the odds of abnormal sperm.
Similarly, a healthy lifestyle featuring a moderate-to-spirited exercise regimen benefits every facet of your body, including the reproductive system and sexual performance. Not surprisingly, more active males have more active sperm -- and more of them.
However, moderation is still essential. Ultra-athletes -- runners, cyclists and swimmers -- who drive themselves to exhaustion on a regular basis can put an excessive strain on the body's major organs and musculature. That can result in diverting your energy (as well as nutrient-rich blood) to recovery and repair, instead of a more balanced state (which includes sperm production). Sustained periods of fatigue can also inhibit normal testosterone levels [source: Mayo Clinic].
Next, we'll examine the effect of stress on sperm.