45 minutes to 2 hours of morning light for weight loss
Great article summing up two studies in the LA Times. In summary, morning sunlight, ranging in length from 45 minutes to 2 hours resulted in improved BMI (Body Mass Index measures), and reduced body fat composition. Among numerous variables investigated, the intensity and timing of morning sunlight were found to correlate most strongly with lower body mass indices. Morning sunlight is known to affect the hormones leptin and ghrelin (the latter known to increase appetite) - and the increased blue-wavelength frequencies of morning light are believed to underpin its efficacy.