"The good news is that people who stay up late in front of the television and computer may be able to undo some of the harmful effects just by going back to a regular light-dark cycle and minimizing their exposure to artificial light at night, " Bedrosian says.

CNN: Unplug! Too much light at night may lead to depression

Over the eight-week period of the experiment the mice in the first and third groups gained almost 50% more weight than those exposed to the natural light-dark cycle.

ECONOMIST: Obesity: The dark side of light | The