This isn't the first study to find a link between morning light exposure and low body weight, but previous research didn't eliminate the possibility that it was a regular sleep cycle that was causing the health benefits.
The new research had 54 adults record their diet and sleep patterns for a week, while also wearing sensor to monitor the timing and intensity of their light exposure throughout the day, Sophie Bushwick writes for Scientific American.
The results, published in PLoS ONE, reveal that people's body weight and appetite was linked to when they saw light each day, regardless of how well they slept and even how many calories they ate.
The scientist write in their abstract: "Exposure to moderate levels of light at biologically appropriate times can influence weight, independent of sleep timing and duration."
And don't worry if you don't live in a sunny part of the world - the research found that getting the majority of your average daily light exposure above 500 lux (that's about half as dim as sunlight on an overcast day, or around the amount you'd get in office lighting or at sunrise or sunset) earlier in the day is all you need.
For every hour later people got the majority of their light exposure, there was a 1.28 increase in BMI.
It's great news for morning people. For the rest of us, maybe it's worth at least turning the lights on or opening the blinds before we hit snooze.