The study suggests owners who charge their smartphones near their bed may have their hormones disrupted by the light the devices emit, leading to weight gain.
Ambient light from charging phones can harm the production of melatonin and stop the body processing food as efficiently, scientists at the University of Granada claim.
Experts at Manchester University are also 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's School of Psychological Sciences, said: "As a 24-hour society sleep deprivation is increasing and we are exposing ourselves to artificial light at night.
"We are trying to extend the waking day into our sleep period and there is not enough protection of sleep."
He said blue light - the kind emitted by phones and laptops - is the kind most likely to disrupt our sleep, and consequently our metabolism.
Dr Kyle said: "There should be a huge public health shift in how we are viewing the sleep period and the hours before it.
"There is not enough protection of sleep. 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."