The time of day when the stress hormone peaks shifts from daytime to nighttime in mice eating a high-fat diet, which is the opposite of what normally happens.

The daily pattern of stress hormone in the mice’s poop is more complicated than just one peak—it has two peaks, and this complexity changes with diet.

The natural daily rise and fall of the stress hormone in the mice’s poop becomes flatter and stays higher all day when they eat a fatty diet.

Even normal mice have a more complicated daily rhythm of stress hormone than just one peak—it has two peaks, and this is true for all mice, not just those on a fatty diet.

Mice that eat a high-fat diet start snacking more during the day—when they normally sleep—and eat less at night—when they normally are active.