Prior research has shown not getting enough
sleep can impact your weight, but new BYU research finds the consistency of
your bed time and wake time can also influence body fat.
Exercise science professor Bruce Bailey
studied more than 300 women from two major Western US universities over the
course of several weeks and found that those with the best sleeping habits had
The main findings from the study, published
online in the American Journal of Health Promotion:
consistent bedtime and, especially, a consistent wake time are related to
lower body fat.
less than 6.5 or more than 8.5 hours of sleep per night is associated with
higher body fat.
of sleep is important for body composition.
Women in the study were first assessed for
body composition, and then were given an activity tracker to record their
movements during the day and their sleep patterns at night.
Researchers tracked sleep patterns of the
participants (ages 17-26) for one week.
The most surprising finding from the study,
according to the researchers, was the link between bedtime and wake time
consistency and body weight.
Study participants who went to bed and woke
up at, or around the same time each day had lower body fat. 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.
Wake time was particularly linked to body
fat: Those who woke up at the same time each morning had lower body fat. Staying up late and even sleeping in may be
doing more harm than good, Bailey said.
“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.
Bailey related consistent sleep patterns to
having good sleep hygiene. When sleep hygiene is altered, it can influence
physical activity patterns, and affect some of the hormones related to food
consumption contributing to excess body fat.
Bailey and his team also found there was a
sweet spot for amount of sleep: Those who slept between 8 and 8.5 hours per
night had the lowest body fat.
Sleep quality also proved to have a strong
relationship to body fat. Sleep quality is a measure of how effective sleep is,
or how much time spent in bed is spent sleeping. Those who had better sleep
quality had lower body fat.
To improve sleep quality Bailey recommended
exercising, keeping the temperature in the room cool, having a quiet room,
having a 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 honour,” Bailey said.
BYU exercise science professors James
LeCheminant and Larry Tucker are co-authors on the paper, as is statistics
professor William Christensen.
(Picture: Sleeping woman from Shutterstock)