Fat men are less likely to have sexual adventures outside a relationship – and not because of a lack of opportunity. The study may sound disappointing to women who like their husbands thin, but the findings are most logical. In the German survey of 1 000 men aged 31 to 69 the relationship of round shape to avoidance of sex outside the relationship was as linear as can be:

• 23 % of men of normal weight
• 19 % of moderately overweight and
• 11 % of fat men admitted interest in having sex with someone else than their relationship partner.

A cost-risk analysis

Being in a healthy, slim shape increases a man’s sexual market value. More women see the man as a suitable partner. Unhealthy body weight lowers a man’s desirability. Contrary to what the research suggests, this means that fat men have fewer opportunities for both casual sex and relationships that provide regular sex.

When caught having an extra-relationship affair, a fat man faces at least the same likelihood of losing the relationship as a slim man would. When without a relationship, it is harder for an overweight guy to find a new affair than it is for a slim fellow. The seeking costs of a new relationship are higher (Laasanen 2008).

The gain is the same but the potential costs are higher.