If you could add cells anywhere in your body, you might pick your brain. More brain cells should make you smarter, right? Well, a new study shows that they might just make you fatter. Because animals that make new nerve cells in a brain region that controls hunger tend to pack on the pounds. The results appear in the journal Nature Neuroscience. [Daniel A. Lee et al., "Tanycytes of the hypothalamic median eminence form a diet-responsive neurogenic niche"]

In the late 1990s scientists found that adult mammals can make new brain cells in an area associated with learning and memory. Since then, studies have shown that new neurons also arise in the hypothalamus, a structure associated with regulating body temperature, sleep and appetite. So, what are those cells up to?

Using techniques to track the birth of new neurons, researchers found that mice fed a high-fat diet make four times as many new cells in the hypothalamus than do animals raised on standard chow. When the scientists eliminated the source of these new cells, the chubby mice gained less weight.

This mechanism might have evolved to encourage animals to store up body fat when food is plentiful. Which used to alternate with lean times. But in these boon times, your brain may be your waist enemy.

—Karen Hopkin

[The above text is an exact transcript of this podcast.]

[Scientific American is part of the Nature Publishing Group.]