How many of us would like to lose a few pounds, but look for external
ways—outside of our bodies—to lose weight? Perhaps we should be
looking more inward, not only at our personal diet and exercise levels,
but the length and level, or phase, of our sleep.
Recently, I read
an article in the American Journal of Physiology – Regulatory,
Integrative and Comparative Physiology. In it, researchers from St.
Luke's-Roosevelt Hospital and Columbia University in New York shed some
light on the link between our length and phase of sleep, and hunger and
weight gain.
The researchers investigated the effects of “sleep
architecture” on hunger to determine whether specific stages of
sleep—not just the duration of sleep—affect the appetite and food
cravings in healthy adults.
What they found is compelling, and
cause for further attention: the length of time of sleep, as well as the
percentage of overall sleep in different sleep stages, are associated
with decreased metabolic rate, increased hunger, and increased intake of
calories, specifically from fat and carbohydrates.
For the study,
head researcher Ari Shechter and his colleagues studied a random sample
of 27 healthy adults between the ages of 30 and 45. The participants
underwent two six-day periods of laboratory observation, during which
they were slept different lengths of time.
During a "habitual sleep"
phase, they were allowed to sleep for nine hours; in the "short sleep"
phase, they were allowed just four hours of sleep. Each of the two sleep
phase studies were separated by four weeks to make sure the
participants fully recuperated, and the women were observed at the same
phase of their menstrual cycle. The amount of time spent in each sleep
phase—stage 1, stage 2, slow wave sleep (SWS), and REM sleep—was
recorded.
For the first four days in both sleep phases, the
participants ate meals to meet their energy requirements for weight
maintenance. On day four, they rated their hunger and level of desire
for different foods. On day five, their resting metabolic rate (RMR) was
measured, and for the final two days of the sleep phase studies, the
participants were allowed to select their own foods.
The
researchers then compared the participants' sleep architectures in both
the short sleep and habitual sleep conditions. They also analyzed the
relationships between sleep architecture, resting metabolic rate, food
intake and food desire ratings.
Shechter and his colleagues found
that sleep duration is important, but sleep composition—the time and
percentage of overall sleep spent in each stage—also plays an important
role in the link between sleep and obesity.
Head researcher
Shechter explained, “Any number of various factors like obstructive
sleep apnea, certain drugs/medications, chronic exposure to short sleep
duration, shift work, jet lag, and changes in the scheduling of the
sleep episode, can affect sleep stage quantity and distribution. Our
data may provide an explanation for the greater obesity prevalence
observed within some of these conditions."
Read the full article, “
Changes in Sleep Architecture Increase Hunger, Eating.”
The results of this study remind me of another study I blogged about not long ago on “
social jetlag,” another reason for all of us to get more sleep.
Social
jetlag is a modern syndrome caused by the discrepancy between our
internal body clock and our social clock. And according to Professor
Till Roenneberg, Ph.D. at the University of Munich’s Institute of
Medical Psychology in Germany, that gap between how much sleep we need
and how much we’re actually getting is contributing to our global weight
gain and the growing worldwide obesity epidemic.
Each of us has a
physiological clock, and that internal clock — also known as our
circadian rhythm — is regulated by daylight and darkness to prompt us to
go to sleep or wake up. We also have a social clock of things that make
up our daily lives, such as our work schedules and social calendars.
The
problem is, in our modern society of too-late work hours and too much
time in front of computer screens, we are listening to our social clocks
more than our physiological clocks, causing a greater sleep gap known
as social jetlag. As a person’s circadian rhythm gets more out of whack,
their physiological clock gets set later and later, keeping them awake
into the night, and feeling chronically tired during the day.
In
their study, Professor Roenneberg and his fellow researchers in Munich
discovered that people with different weekday and weekend sleep
schedules—i.e., those with more social jetlag — were three times more
likely to be overweight. That is a significant increase worth repeating:
Three times more likely to be overweight!
Furthermore, the body
mass index (BMI) of the overweight participants tended to increase as
the gap between their weekday and weekend sleep clocks widened.
I
applaud the efforts of Roenneberg and his team for their work in
particular, because they are bringing a public awareness of a growing
syndrome that is affecting many people worldwide — not just shift
workers or those with irregular work schedules.
So, why does
social jetlag cause weight gain? One of the theories is that late hours
encourage irregular meal times and late-night eating, when the body has
more difficulty digesting and metabolizing food. That translates into
body fat. Another is that chronically tired people are less likely to
exercise and more likely to smoke and drink, further contributing to
weight gain.
Whatever the causes, it is in all our personal best
interests to become more aware of our own physiological clocks and get
more restful sleep. Doing so can help us all maintain a healthy body
weight, avoid many health problems, feel better and live happier, more
productive lives.
So, now that you have this new knowledge about
sleep, weight gain, I suggest you give yourself a wonderful personal
gift: get more sleep, especially during the holiday season, when many
people are overeating and busier than usual. Also spend more time
outdoors and exercise. More and better sleep is one of the best gifts
you can give yourself for the holidays.
Read Professor Roenneberg and his team’s full report entitled, “
Social Jetlag and Obesity,” published in the May 10 issue of Current Biology.
David O. Volpi, MD, PC, FACS 
By David Volpi, M.D., P.C., F.A.C.S. 
If you or someone you love has a heart failure condition, not
sleeping well can double the likelihood of being hospitalized, according
to new research by the European Society of Cardiology.
