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 Among some 1,600 people in the UK, researchers found that those who
slept more than eight hours a night had lower body mass index (BMI)
- a measure of weight relative to height - and slightly smaller
waists when compared to people who slept less than seven hours.
Longer sleepers also had slightly higher levels of HDL “good”
cholesterol.
“Most of the findings are in line with what experimental sleep loss
studies have shown. I think maybe a plus of this is that obviously
it's a much larger sample than something you would see in a
laboratory,” Namni Goel, a sleep researcher at the Perelman School
of Medicine at the University of Pennsylvania in Philadelphia who
wasn’t involved in the study.
For the study, published in PLoS One, Gregory Potter of the School
of Medicine at the University of Leeds in West Yorkshire, and his
colleagues analyzed four years’ of data from a national diet and
nutrition survey that also tracks other health and lifestyle habits
among people in England, Northern Ireland, Scotland and Wales.
The available data included self-reported sleep records and food
diaries for 1,615 adults, along with height and weight and blood
pressure readings. In addition, about half of the participants
agreed to provide blood samples so the study team could examine
various measures of metabolic health such as cholesterol, blood
sugar and thyroid hormone levels.
Researchers divided participants into three groups based on their
average sleep duration. The bottom third had an average of 5.88
hours of sleep per night, with a range of plus or minus 52 minutes.
The middle third had an average of 7.26 hours of sleep per night,
plus or minus about 15 minutes, and the top third got an average of
8.44 hours of sleep at night, plus or minus 40 minutes.
The study team found that people in the top third for sleep duration
had BMIs that were about two points lower – the equivalent of
roughly 7 pounds (3.2 kilograms) – compared to people in the lowest
third.
The longest sleepers also had waist circumferences averaging 1.6
inches (4 centimetres) smaller than the shortest sleepers.
Each extra hour of sleep was tied to a third of an inch (0.9 cm)
difference in waist size and 0.46 of a BMI point, the study team
reports.
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There were slight improvements with more sleep in some blood
markers, but after researchers adjusted for other factors, the
differences were not statistically significant, meaning they could
have been due to chance.
The study team also didn’t find any association between sleep
duration and diet or calorie intake, although Goel noted that food
and sleep diaries are often inaccurate.
There are currently ongoing studies trying to figure out the
mechanisms behind sleep and weight issues, said Goel, but she thinks
it’s clear the source of the weight gain is overeating.
“Some of it is that when people are sleep deprived, they tend to go
for high calorie, fatty, good tasting foods, and one of the ideas
behind that is that it may be that some of the reward centres in the
brain are affected by sleep loss. Those centres stimulate people to
go for those higher fat foods,” she said by email.
Dr. Samuel Klein, director of the Center for Human Nutrition at
Washington University School of Medicine in St. Louis, noted that
short experimental studies in research units show that short sleep
increases hunger, increases appetite and increases food intake.
Klein, who wasn’t involved in the study, said people can get better
sleep by focusing on a combination of two things: getting more sleep
for the hours spent in bed and increasing the time they allocate for
sleeping.
"Things like keeping the room where you sleep cool and dark, don't
have a lot of lights on before bedtime, keep it dark, don't watch TV
in bed," he said by email.
“Go to bed earlier, wake up later. Those are things that can be done
by really making sleep a priority,” Klein added.
SOURCE: http://bit.ly/2hnMBDT PLoS One, online July 27, 2017.
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