Having a glowing smartphone in your bedroom at night could do more than interrupt your beauty sleep – it could also make you fat, researchers have warned.

They say that our bodies need pitch-black dark to produce the right levels of a hormone involved in regulating the conversion of food and drink into energy.

It means ambient light from street lamps can disrupt the release of melatonin and prevent us burning food as efficiently.

Charging your phone, tablet or laptop in your bedroom at night could make you gain weight because the blue light emitted by the gadgets harms the production of 'sleep hormone' melatonin, a study found

But scientists say short-wavelength blue light, which is emitted by some devices when they are charging, is the most disruptive to sleep – and consequently our metabolism.

Although it is not bright enough to light up a room, it still disrupts our bodies, they said. A team at the University of Granada in Spain discovered that injections of melatonin helped combat obesity and diabetes in rats by helping to regulate their systems.

Now experts at Manchester University are investigating how regulating sleep patterns might help patients who already have diabetes, a disease often linked with obesity.

Dr Simon Kyle, a sleep researcher at the university, said: ‘A lot of people are interested in this at the moment given that as a 24-hour society, sleep deprivation is increasing and we are exposing ourselves to artificial light at night.

HOW USING GADGETS AT NIGHT INCREASES HUNGER Using a computer or smartphone at night can cause us to pile on the pounds, research found. The study found a link between blue light exposure - blue light is emitted by smartphones and tablets - and increased hunger It found that exposure to the light increases hunger levels for several hours and even increases hunger levels after eating a meal. Results of the US study show that blue-enriched light exposure, compared with dim light exposure, was associated with an increase in hunger that began 15 minutes after light onset and was still present almost two hours after the meal. Study co-author Ivy Cheung, of Northwestern University, in Chicago, said: ‘A single three-hour exposure to blue-enriched light in the evening acutely impacted hunger and glucose metabolism. Advertisement

‘We are interested in how an alteration in the sleep-wake pattern may be involved in the onset of diabetes and obesity and if, when you improve the timing of sleep you can also have a positive effect on conditions like diabetes and obesity.

'There is a lot of research showing we are meant to be asleep at night when darkness falls and melatonin rises and when the sun rises the melatonin is blocked by the sun. This light-dark cycle is good for our bodies to predict changes in the environment.

‘So if you start sleeping shorter, or receive light at the wrong time late into night, it disrupts melatonin secretion and that could contribute to alterations in metabolism.’

Blue light is the most damaging because it keeps the mind buzzing, he added.

Earlier this year, leading scientists from universities including Oxford, Cambridge and Harvard, warned that a lack of sleep can cause severe health problems, such as cancer, heart disease, Type 2 diabetes and obesity, because it upsets the body clock.

They said the modern phenomenon was being fuelled by our use of devices late at night which emit blue light.

Dr Kyle advised turning off smartphones, tablets and desktop computers a couple of hours before going to bed to reduce exposure to artificial light.

He added: ‘There is strong basic science and data to show the association between sleep interference and disease.

‘If you can have complete darkness at night time you might be able to recreate time’s pre-industrial period and have a stab at improving the obesity epidemic.’