Losing weight by the dawn’s early light

Posted by Liz on Apr 4, 2014 in weight, weight gain | 0 comments

Did you read Monday’s post about nighttime light exposure and weight gain? Today’s post provides broader context in that there are data showing that greater exposure to light during the daytime may influence body weight independently of when you sleep and how long you sleep for.

In a small study conducted by University of Northwestern researchers (which calculated dietary intake, sleep and light exposure over a week’s time),  people exposed to the most intense light levels earlier in the day had lower BMIs. Moreover, the later the hour of moderate light exposure, the higher the BMI.  A possible reason is that natural changes in light intensity that occur in the morning versus in the afternoon/evening might have a role in influencing weight. This time of day is the time when the amount of blue light (light with a shorter wavelength) is highest; blue light appears to strongly influence circadian rhythms, which in turn, influences metabolism. Exposure to blue light during the day can also positively alter the secretion of melatonin at night, helping to keep the weight off.

Although these findings don’t show cause and effect, they suggest that not getting sufficient light at the correct times of day may be affecting your weight in ways that you’ve never considered. Future research may tease out the way that light may work to modify weight gain. In the interim? Spring has sprung in our part of the world and the days are growing longer. Get out of the house earlier and for longer periods of time; who knows? It may help your weight as well as your mood.