To explore this connection, researchers analyzed U.S. military satellite images of nighttime illumination around the globe and country-level data from the World Health Organization (WHO) on the prevalence of overweight and obese people.
Artificial light at night contributed to excessive weight in men and women about as much as eating junk food, the research team reports in the International Journal of Obesity.
"Because of artificial light at night, we often eat in the wrong time, that is, after the natural dusk, when metabolic processes slow down," said N.A. Rybnikova of the University of Haifa in Israel.
The study doesn't prove light bulbs cause obesity, and scientists aren't yet certain how lamps or the glow from gadgets like tablets and televisions might influence how much people weigh, researchers caution.