Dads-to-be pile on the pounds too

I knew there would have to be an evolutionary explanation for all that weight I put on when my wife was pregnant. Of course the study involves monkeys and has not been applied to human fathers-to-be, but now it's my story and I'm sticking with it until proven otherwise!

In studies on two groups of monkeys, marmosets and tamarins, both small, monagomous primates, the father to be gains 10% of his body weight during the mate's pregnancy.

The males' weight gain is probably a result of their producing greater levels of prolactin – the same hormone that encourages milk production in the females. “Our earlier studies showed that prolactin levels increase in males halfway through pregnancy, when the females experience a hike in corticosterone – a hormone involved in sending and receiving pheromones,” she adds.

A couple of caveats regarding the application of these results to humans. First, increased prolactin level alone is not a associated with weight gain in humans. Secondly, prolactin is associated with good fathering practices in some other animal groups but a direct link in humans and other primates has not yet been verified

It would be great to look at hormone levels in good and bad fathers but it’s very hard to get the data on men who abandon their babies...

As for me, I put on about 5% of my weight during the pregnancy and another 10% afterward - something tells me my excuse isn't going to hold up to scrutiny.