Sharing this notation from the AANP:
MON., NOV. 18, 2013: JUST-RELEASED NATURAL HEALTH STUDY: CONSISTENT BEDTIME, WAKE TIME, LINKED TO LOWER BODY FAT AND WEIGHT: New research shows that consistency in the time that an individual goes to bed and wakes up can result in lower body fat and healthier weight. (Prior research linked inadequate sleep to accumulation of fat and weight.) Scientists studied over 300 women, aged 17 to 26, day and night, over the course of several weeks and found that those with the best sleeping habits had healthier weights. The findings show that a consistent bedtime, and especially, a consistent wake time are related to lower body fat; getting less than 6.5 or more than 8.5 hours of sleep per night is associated with higher body fat; and the quality of sleep is important for body composition. Those with more than 90 minutes of variation in sleep and wake time during the week had higher body fat than those with less than 60 minutes of variation. Those who slept between 8 and 8.5 hours per night had the lowest body fat. This study was posted online in advance of future publication in the American Journal of Health Promotion. It is at http://tinyurl.com/kyopgnn where it can be accessed online for a fee.