A new study revealed that sleeping with lights on could increase one's risk of adding body fat.
Researchers at the Institute of Cancer Research in London looked at questionnaire data from 113,000 women aged 16 and above collected between 2003 and 2012. The participants rated the amount of light in their bedrooms from light (light enough to read or see across the room), medium (light enough to see the hand but not across the room), and dark (cannot see anything). The analysts then compared the participants' responses to their body mass index (BMI) and body fatness. Other factors such as age, childbirth, income, job, alcohol intake, smoking habits and sleep duration were also taken into account.
After careful analysis, the researchers concluded that those sleeping in dark bedrooms were 21 percent less likely to become obese than those sleeping in light bedrooms.
"Metabolism is affected by cyclical rhythms within the body that relate to sleeping, waking and light exposure," said Prof. Anthony Swerdlow, co-author of the study from the Institute of Cancer Research, in a press release.
Some theories were formulated to explain the link between body fat and bedroom light including the idea of "body clock disruption." Our body recognizes that it should be active during the day and at rest during night time. Bedroom light disrupts the body clock causing a delay on the production of the sleep hormone. Another was that obese people are heavier sleepers, so they prefer sleeping on lighter bedrooms, according to the analysis of NHS Choices.
However, the researchers clarified that further study is needed to fully establish a link between bedroom light and obesity. The study failed to explain how differences in light levels at night affected body fat.
"There might be other explanations for the association, but the findings are intriguing enough to warrant further scientific investigation," said Prof. Swerdlow during an interview with the BBC.
Details of the study were published in the American Journal of Epidemiology.
