Can morning light help you stay lean?

Night owls, beware -- hitting that snooze button every morning could be sabotaging your weight loss goals.

Intriguing new research suggests that getting an optimal amount of morning light can help a person stay lean, and it doesn't matter if that light comes from the sun or a light bulb.

Researchers from Northwestern University found a connection between the amount of light exposure a person gets between the hours of 8 a.m. and 12 p.m. and their body mass index (BMI).

This correlation was noted independent of how many calories a person consumed throughout the day. And in fact, light exposure was the strongest predictor of BMI compared to other factors such as age, gender, exercise, sleep and season.

"We found that the earlier this light exposure occurred during the day, the lower individuals' body mass index," study author Kathryn Reid tells NPR.

Researchers found that for every hour that light exposure was delayed, BMI rose by 1.28 points.

The study, published in the journal PLoS One, examined 54 volunteers who wore a wrist monitor that measured their light exposure and sleep patterns. The average age of the volunteers was 30 and they tended to be night owls compared to your average American.

The results suggest that the ideal amount of light exposure is at least 500 lux. As a point of comparison, an office environment averages about that amount and even an overcast day reaches more than 1,000 lux.

Previous studies show that keeping our sleep patterns in line with the natural cycles of light-dark plays an important role in regulating our circadian rhythm, which ultimately affects our metabolism and our waistlines.

Reid believes about 20 to 30 minutes of morning light would be enough to affect BMI.

It's worth noting, however, that a growing body of research suggests BMI does not provide the best measurement of one's health, nor does it accurately assess a healthy body weight.