Morning light can be a key to weight loss, according to new research. A small study found that people who were exposed to sun earlier in the day were generally leaner.

A total of 54 adults were included in the study. Of the 54 participants, 26 were male and the average age was 31. A monitoring device worn on the wrist measured light exposure as well as sleep mid-point and sleep duration for seven days.

The study found that there was a difference in the weight of people who were exposed to sunlight in the morning rather than later in the day, with the former group tending to be leaner than the rest.

According to the new study results, people who are exposed to a minimum of 20 to 30 minutes of bright light in the morning are likely to have a lower body mass index. It is believed that this is due to the way that light impacts the brain. It is also thought that morning light plays an important role in waking people up and elevating their moods, and can be a catalyst to make healthier decisions throughout the day.

Dr. Phyllis Zee, lead study author and director of the sleep disorders center at Northwestern University Feinberg School of Medicine in Chicago, said, “We were very interested in looking at the relationship between lighting and how that may be affecting your weight.” She continued, “This is an early study, but we did indeed see a fairly robust association between the amount of light and the timing of light, and weight.” However, Zee acknowledged that the study only discovered a connection between early light exposure and lower weight, rather than a cause-and-effect link.

Zee explains that the benefits of morning light are evident. “It affects hormones that regulate appetite,” she says, continuing on to say, “It affects hormones and neurotransmitters that regulate the sleep-wake cycle.”

It is possible that the color blue may play an important role when it comes to morning light. Zee notes that, “It’s a more powerful stimulus for your brain than let’s say the red light or the orange light we get later in the afternoon.”