To maximize your chances of fighting flab, new research offers some simple advice: Wake up early and go outside.
People who loaded up on light exposure at the beginning of the day were most likely to have a lower body mass index, according to a study published this week in the journal PLOS ONE. That relationship between morning light and BMI was independent of how many calories the study participants consumed.
It may sound crazy, but there is sound scientific evidence to back up the link. Circadian rhythm plays an important role in regulating metabolism, and studies have shown that exposure to morning light can influence body fat and the hormones that regulate appetite.
In one study, for instance, sleep-deprived subjects whose levels of the hormones leptin and ghrelin were out of whack saw those levels improve after being exposed to light for two hours after waking up. In another study, obese women who were exposed to bright light for at least 45 minutes between the hours of 6 a.m. and 9 a.m. dropped some of their body fat after three weeks. And studies in animals have found that altering light exposure changed their metabolism, resulting in weight gain even when the animals consumed the same amount of calories as before.
With all this in mind, researchers at Northwestern University’s Feinberg School of Medicine in Chicago persuaded 54 volunteers to wear a wrist monitor that measured their light exposure (including its timing and intensity) as well as their sleep patterns. The volunteers were also asked to keep a detailed log of everything they ate and drank during a seven-day period.