On a biological level, men have evolved to focus on the features of a woman that suggest fertility – large breasts, a small waist and full hips indicate that a woman is young, healthy and probably not already pregnant.
Experts have discovered that high levels of the hormone oestradiol make women more likely to cheat. The reason? It creates bigger breasts and smaller waists. As a result, they tend to get more attention and, therefore, have more sexual opportunities.