Study: Does When You Eat Matter More Than What You Eat?

New studies at Penn say yes.

You know that bag of chips or bowl of popcorn that tastes so darned good at midnight? Scientists at Penn’s Perelman School of Medicine say such nighttime snacks just might be why America’s obese. New studies conducted on mice indicate more strongly than ever that it’s not what you eat that makes the difference; it’s when.

The scientists were able to induce “energy storage”—the polite word for fat—in mice via a “relatively modest shift in food consumption into what is normally the rest period for mice,” according to research associate Georgios Paschos. “Our mice became obese without consuming more calories”— every dieter’s worst nightmare.

The researchers took two different approaches to test their thesis. In one, they broke the “clock gene” in fat cells that normally causes mice, which are nocturnal—as the ones in my kitchen attest—to eat at nighttime. This resulted in metabolic changes similar to those that occur in what’s called “night-eating syndrome” in people, which, alas, has been shown to cause obesity. The changes disrupt the complicated act of balancing energy levels in the body: Breaking the fat-cell clocks altered the release of certain unsaturated fatty acids into the blood stream, so that signals telling the hypothalamus the body was sated never got through.

In the second set of studies, researchers were able to fatten normal mice simply by reproducing the altered eating patterns of the mice with broken fat-cell clocks. “Our findings show that short-term changes have an immediate effect on the rhythms of eating,” according to Garret FitzGerald, director of Perelman’s Institute for Translational Medicine and Therapeutics. “Over time, these changes lead to an increase in body weight.”

One implication of the new work? If you’re changing your eating patterns to keep company with a late-eating partner, you, too, could end up packing on pounds.