Too much light in the bedroom may cause weight gain

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A study shows that sleeping in a room where there is too much light may be linked to an increase in weight gain.

A team based at the Institute of Cancer Research in London found that women had bigger waistlines if the light in their bedroom allowed them to see across it at night.

They warn that there is insufficient evidence to advise people to turn off their lights or buy heavier curtains.

The study involving 113000 women has been published in the American Journal of Epidemiology.

During the study the women were requested to rate the level of light in their bedrooms at night. The choices they were offered included:

• Sufficient light to read
• Insufficient light to read, but sufficient to see across the room
• Enough light to see your hand in front of you, but not to see across the room
• You wear a mask or it is too dark to see your hand in front of you

The answers to the questions were compared to a range of obesity measures. It was found that the waist-to-hip ratio, waist circumference and body mass index were all higher in those females who had lighter rooms.

Professor Anthony Swerdlow, of the Institute of Cancer Research, stated that there is a link between the reported nightly light exposure and obesity, and overweight. However, he stated that there is not enough evidence to determine if darkening your room would affect your weight.

He stated that there may be other explanations for this link, but the current findings are interesting enough to warrant additional scientific investigation.

One possible explanation offered may be that the body clock is disrupted by the light. This comes from our evolutionary past when humans were active during the day and rested at night when it was dark.

Light is said to alter physical strength, mood and the method in which food is processed during a 24-hour period.

Artificial light has been known to cause disruption to the body clock because it delays the production of the sleep hormone, known as melatonin.

The Surrey Sleep Centre’s Professor Derk-Jan Dijk said that no harm would come to those who make their bedrooms darker. He said that people are not always aware of the amount of light in their bedroom and that they should do an assessment and decide on how to darken it. Street lights, certain alarm clocks and standby lights on electrical appliances could offer light to a room. He said that the overall study indicates the importance of darkness.

This study was funded by Breakthrough Breast Cancer and the results come from a long-term study to determine the risk factors linked to breast cancer. Obesity is a factor known to increase the chances of the disease.

Dr Matthew Lam from the charity stated that it was too early to make a suggestion that sleeping in the dark will prevent obesity, a known breast cancer risk factor, however, the link is interesting.

He said that scientists are learning more and more about the lifestyle, genetic and environmental factors that affect the risk of breast cancer, but it is still not possible to predict who is at risk of breast cancer. For those women who have been diagnosed with this disease, it is not possible to stipulate the cause.

Image Credit: Juan Antonio Flores Segal

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