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February 1, 2006

Tamarins, Marmosets and Me: Tackling a Weighty Problem

I'm scared to get on the scale.

I'm absolutely convinced I've put on some pounds in the last few months. It's not just all the bad things I ate over the holidays; there's something else going on, and I don't like it. But at least I have a scapegoat for my woes: pregnancy.

No, silly, I'm not pregnant. But Susanne is. We've known about the pregnancy since November, and in the last few weeks, she's really began to show, belly-wise. Meanwhile, I've been feeling like I've been putting on the pudge over the same period of time. Was the problem that I was eating the extra calories in tandem with Susanne? Sometimes, perhaps, but certainly not always. When she has a craving for a root beer float, for example, I support her by drinking a diet root beer while she enjoys the real thing with some Ben & Jerry's floating on top. (Usually, at least. I'm trying.) So her change in diet might account for some of this sympathetic weight gain, but not the whole kit and kaboodle.

Of course, it's often said that men put on weight while their wives/partners are pregnant, but it's not well documented scientifically. Today's online edition of New Scientist, though, sheds some light on why I'm having a hell of a time shedding off those extra pounds.

According to the article, researchers at the University of Wisconsin-Madison National Primate Research Center have discovered that the males of certain primate species gain weight while their mates are pregnant. The scientists studied pairs of common marmosets and cotton top tamarins, measuring their weight during the females' gestation period. The males gained weight, even though they weren't given access to additional food.

Tamarins, Marmosets & Me: Destined for sympathetic weight gain?
Photos of tamarin and marmoset courtesy of Wikimedia Commons.
Photo of me courtesy of me.

"We found that the males gained on average an extra 10% of their body weight during the pregnancy," explained researcher Toni Zeigler. "Weight gain is beneficial for the males because it prepares them for the higher energetic costs involved after the babies are born.... The monkeys usually have twins and they are born fairly large - about 20% of their adult weight - and the father mostly has to carry them on his back."

What's causing all this weight gain? The scientists suspect the hormone known as prolactin. In females, increased prolactin leads to breast milk production, among other changes. For males, prolactin output causes weight gain.

"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 added. "We know that prolactin promotes paternal care from studies in birds, where higher levels of the hormone cause the fathers to feed the chicks more often, but we don't know what other roles it has in primates or humans."

"But marmoset and tamarind males are excellent fathers and remain monogamous for life, so it could help explain what biological changes are necessary in humans to produce a good dad," Zeigler concluded.

So maybe these extra pounds are Mother Nature's way of forecasting that I'm going to be an excellent father. Then again, maybe she's just annoyed that our cat Winston spends more time sleeping on our treadmill than I spend running on it.... -andy

Posted by acarvin at February 1, 2006 1:50 PM

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