Sleeping well at night means proper sleeping environment — reduced noise, comfortable mattress, and a dark room. For those who are afraid of the dark, a night light may be the best way to fall asleep, but it could wreak havoc on your health. According to a recent study published in the American Journal of Epidemiology, sleeping in a room with too much light may increase body mass index (BMI) and waist size for women.

"Metabolism is affected by cyclical rhythms within the body that relate to sleeping, waking and light exposure," said Professor Anthony Swerdlow from the Institute of Cancer Research in London, Medical Daily reported with reference to The Telegraph. Dating back since evolutionary beginnings, being active when it's light in the day and resting when it's dark at night is part of our human circadian (24-hour) body clock. Light has the ability to alter moods, physical strength, and even the way we process food in a 24-hour cycle. Disruption of sleep and circadian rhythms via light exposure could be a contributing factor to the rise in obesity.

Emily McFadden, co-author of the study and a visiting researcher at the institute, along with her colleagues, sought to investigate whether the disruption of circadian rhythms by exposure to light at night (LAN) could contribute to weight gain in women. Data was drawn from the Breakthrough Generations Study, a cohort study of women aged 16 years or older who were recruited during 2003-2012.

The women were asked to rate the amount of light in their bedrooms at night as: light enough to read; light enough to see across the room, but not read; light enough to see your hand in front of you, but not across the room; and too dark to see your hand, or you wear a mask.

The findings revealed the odds of obesity increased with increasing levels of LAN exposure.

The researchers do suggest artificial light can contribute to weight gain by delaying the production of melatonin — the sleep hormone.