The researchers found that mice exposed to dim light at night for eight weeks experienced an increase in body mass about 50 percent higher than other mice living in a normal light-dark cycle. According to Laura Fonken, director of the study, "although there were no differences in activity levels or daily food consumption, the mice that lived with light at night were fatter than the others." The authors believe that birth alters levels of the hormone melatonin , which is involved in metabolism and could also disrupt the expression of circadian genes that help control when and when animals feed. ? Timing of eating is critical to gaining or not gaining weight, "says Fonken.
Overall, the results could offer an explanation for the current obesity epidemic in Western countries . "Light at night is an environmental factor that could be contributing to obesity in ways that people do not expect," explains Randy Nelson, co-author of the study. Researchers have identified prolonged use of the computer and television as risk factors of obesity.
