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 Studies have shown that eating later in the day ups your risk of
weight gain. However, the impact of a person’s body (biological)
clock - independent of the time of day - has not been tested until
now, according to Dr. Andrew McHill of Brigham and Women’s Hospital
in Boston and colleagues.
“Our findings could be considered a reason not to eat right before
going to sleep, but they’re also a reason not to eat later in the
evening, even if you are planning to go to bed at a later time,”
McHill told Reuters Health by email.
The team recruited 110 college students ages 18 to 22 (about 60
percent male) for a 30-day study of sleep times and food intake.
The students completed questionnaires about their sleep habits at
the outset of the study, as well as daily electronic sleep-wake and
exercise diaries. They also wore motion monitors throughout the
study to help track sleep-wake timing.
For one week during the study, participants used a mobile phone app
to time-stamp, document and record their food intake during their
regular routines.
They were also evaluated for one night at the hospital to see what
time their level of the hormone melatonin began to rise - which
marks the beginning of a person’s biological night - and to assess
their body composition (i.e., muscle mass and fat).
Melatonin onset timing was similar for both lean participants and
those with a higher percentage of body fat, according to the
American Journal of Clinical Nutrition study, online September 6.
However, those with a higher percentage of body fat - 8.7 percent
higher in women and 10.1 percent higher in men - ate most of their
calories about an hour closer to the time of melatonin onset than
did lean participants.
There was no relationship between body composition and when (clock
hour) they ate, how many calories they consumed, what kind of food
they had, their exercise or activity level or sleep duration.
“While it’s not possible to know the timing of your melatonin onset
without having it measured very precisely in dim lighting, we tend
to think that melatonin levels rise about two hours prior to
habitual sleep onset,” McHill explained.
What about waking up and eating a snack in the middle of the night?
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“This would also be a time when melatonin is high and your body
clock is promoting sleep and fasting,” he said, “so we would
consider that a time that food consumption could lead to higher body
fat if done repeatedly over a long period of time.”
McHill cautioned that the findings don’t show cause and effect. To
do that, he said, “randomized controlled trials that include
altering the timing of meals of the exact same food content in
relation to melatonin timing (e.g., providing meals within four
hours of melatonin onset or restricting calories to when melatonin
concentrations are low) are needed.”
It’s also important to study groups other than college students, and
the team has already begun to track meal timing in older and ill
populations.
Dr. Eric Feigl-Ding, a nutritional epidemiologist at Harvard Chan
School of Public Health in Boston who was not involved in the study,
told Reuters Health he agrees that “the takeaway is that eating
earlier before bed may be better” - perhaps as much as 4 to 5 hours
earlier.
However, “actual experiments to show direct long-term weight loss
and health benefits from consistently eating earlier before bed are
needed,” he added by email.
“Be vigilant of your food intake as time to sleep approaches,” Dr.
Jocelyn Cheng, a neurologist at NYU Langone Health in New York City
urged in an email to Reuters Health.
“If you notice yourself eating more during this period compared to
earlier in the day, consider redistributing your meals, snacks
included,” said Cheng, who was not involved in the study.
SOURCE: http://bit.ly/2wUGGu3 American Journal of Clinical
Nutrition, online September 6, 2017.
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