Constant bedtime and wake-up time leads to lower body fat in women, according to a Brigham Young University study. Researchers found that people with good sleeping habits had healthier weights.

For the study, Bruce Bailey, an exercise science professor studied 330 women from BYU and Utah Valley University over several weeks. Participants, aged 17 to 26, were first examined for body composition, and then were asked to record their movements during the day and sleep patterns at night using an activity tracker. Bailey observed sleep patterns of the participants for a week.

He found that participants who slept and woke up at the same time everyday had lower body weight. On the other hand, participants with a 90-minute difference in sleep patterns had higher body weight than those whose bedtime or wake-up varied by less than 60 minutes.

Bailey said that wake-up time was mainly linked to body fat. Those who wake up at the same time had lower body fat.  Staying up late and sleeping in does more harm than good.

 "We have these internal clocks and throwing them off and not allowing them to get into a pattern does have an impact on our physiology," Bailey said in a statement.

When a sleep pattern is disturbed, it can affect physical activity patterns and hormones related to food consumption, particularly those that signal a person when he/she is full.

The study also found that sleeping less than 6.5 or more than 8.5 hours results in higher body fat. Lowest body fat was observed in people whose sleep duration ranged between 8 and 8.5 hours.

 "I think we have our circadian rhythms, this internal clock, and when we consistently get up at different times it makes it difficult for our body to get into a rhythm," Bailey told Salt Lake Tribune.

Apart from sleep patterns and duration, sleep quality also affects the fat content in our body. People with good sleep quality had lower body fat.

In order to improve sleep quality, Bailey recommends exercise, maintaining a cool temperature in the room, a quiet and dark room, and using beds only for sleeping.

"Sleep is often a casualty of trying to do more and be better and it is often sacrificed, especially by college students, who kind of wear it as a badge of honor," Bailey said.

The finding has been published online in the American Journal of Health Promotion.