A new study has found that people who sleep with lights on or while watching TV or using mobile phones tend to put on weight.

The researchers of Leiden University Medical Centre, Netherlands found out in a survey that artificial lights can disrupt the body clock and also the brown fat cells that burn calories. It is advisable to switch off all lights and gadgets at bedtime, the Mirror reported.

The researchers mentioned that on an average people stay online for about 20 hours a week and for 16 to 24-year-olds this figure rises to more than 27 hours.

Sander Kooijman, a researcher said that the increasing prevalence of obesity was associated with a disrupted sleep-wake pattern in humans and coincides with the availability of artificial light.

The survey is published in National Academy of Sciences journal Proceedings.