A study out of Northwestern found that men and women who got most of their daily light exposure between 8 am and noon had significantly lower BMIs than those who got the bulk of their sun exposure later in the day. The researchers ruled out the participants’ physical activity level, caloric intake and age as mitigating factors. They reason that the timing of sun exposure has such a big effect on BMI because sunlight plays a major role in regulating our circadian rhythms, which help control metabolism. To get your weight-maintaining 20 to 30 minutes of morning sun per day, try walking to work, or schedule early meetings in the room with the biggest windows.

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