Researchers at Northwestern University in Illinois have found a link between light exposure during sleep and obesity.
Turn off your phone, TV and lights before bed if you want to stay slim, scientists say. They tracked the data of 552 people aged 63 to 84. All volunteers were asked to track exposure to light, including at night, for a week. To the shock of the researchers, only less than half consistently had a five-hour period of darkness.
The results showed that 40.7% of people exposed to light for five hours were obese compared to 26.7% in the no light group. About 17.8% in the light-exposed group had diabetes, twice as many as in the other group (9.8%). A similar difference was found between groups when it came to the incidence of hypertension.
The differences were significant when other potential risk factors were controlled for. The study was observational, meaning the team was unable to prove that light exposure causes obesity, diabetes, or hypertension. However, experts believe that falling asleep with the lights on can reset the biological clock. This can lead to disruption of hormone levels that have a domino effect and cause people to consume more food.
While the study only looked at older adults, previous studies have shown similar effects in younger generations.
But other experts argue that the light emitted by smartphones and tablets is much weaker than natural light at dawn. They say that the problem is related to the increased activity of people who use gadgets before bed or instead of sleep.