Want to affair-proof your marriage? Then first, you've got to understand what makes men cheat. Hear it from the relationship experts as they dish out on the number one reason for infidelity and ways to protect your relationship.

Why men cheat

The XY species: They're notorious for their roving eyes and their obsession with bikini-clad models, so connect the dots, and the automatic assumption is that men cheat for the sex.

But here's the surprising truth: According to marriage counselor M. Gary Neuman, author of The Truth About Cheating, who surveyed 200 cheating and non-cheating husbands, the number one reason for straying is emotional dissatisfaction, which an astounding 48 percent of cheating men listed as the main trigger. Only 8 percent of men listed sexual dissatisfaction as the primary factor in their infidelity. In fact, just 12 percent of cheating husbands said their mistress was more physically attractive than their wife.

Many of these "emotionally dissatisfied" men claim they don't feel appreciated or wanted. And Neuman believes it is this feeling of underappreciation and lack of thoughtfulness that far outweigh any other reason for infidelity.