A specific molecule that predisposes mice or humans to fidget may also be linked to a decreased likelihood of obesity, according to a study conducted by scientists from Germany and the United States and published in the journal Cell Metabolism.

"The molecule is called Bsx and is required for spontaneous activity," said lead researcher Mathias Treier. "Mice that lack Bsx in their hypothalamus are a lot lazier than normal mice. They show less spontaneous activity and less food seeking behavior."

Researchers from the European Molecular Biology Laboratory (EMBL), the German Institute for Nutrition (DIFE), Potsdam, and the University of Cincinnati examined the effects of Bsx in the brains of mice. They found that mice who lacked Bsx in their brains showed less spontaneous physical activity -- in other words, fidgeting -- and also perceived their body's hunger signals differently.

Both spontaneous physical activity and food intake are regulated by a part of the brain called the hypothalamus. This is not coincidental; fidgeting behavior is strongly linked to food-seeking behavior. Thus, when the body is hungry, fidgeting increases and the animal is driven to go find more food.

Bsx regulates the way that hunger-promoting hormones are expressed in the body. Without Bsx in the brain, the body produces less of these hormones. In addition, the researchers believe that Bsx is required for brain cells to properly interpret hunger signals from the rest of the body. Without the molecule present, the brain -- and thus the animal -- does not know that it needs food and does not feel hungry.

The researchers believe that Bsx production may be genetically controlled.

"Bsx is conserved across species and very likely plays a similar role in controlling body weight in humans," says Maria Sakkou of the EMBL. "Differences in Bsx activity between individuals could help explain why some people are intrinsically more active than others and less susceptible to diet-induced obesity. Bsx might be the key to why the same diet makes one person fat, while leaving another unaffected."

Aside from hunger-regulating effects, of course, increased physical activity helps stave off obesity in its own right.

"We're spending energy by doing that [fidgeting]," Treier said, "and this is, of course, one of the key factors in energy balance."