What Triggers Those
Late-Night Snack Cravings?
From ScienceDaily.com
A
study published in the most recent version of the journal Obesity found
that the body's internal clock, the circadian system, increases hunger and
cravings for sweet, starchy and salty foods in the evenings.
While the urge to
consume more in the evening may have helped our ancestors store energy to
survive longer in times of food scarcity, in the current environment of
high-calorie food, those late night snacks may result in significant weight
gain.
"Of
course, there are many factors that affect weight gain, principally diet and
exercise, but the time of eating also has an effect. We found with this study
that the internal circadian system also likely plays a role in today's obesity
epidemic because it intensifies hunger at night," said Steven Shea, Ph.D.,
director for the Center for Research on Occupational and Environmental
Toxicology at Oregon Health & Science University and senior author on the
study. "People who eat a lot in the evening, especially high-calorie foods
and beverages, are more likely to be overweight or obese."
Indeed,
eating a lot in the evening can be counterproductive since the human body
handles nutrients differently depending on the time of day. For example, sugar
tolerance is impaired in the evening. Additionally, consuming more calories in
the evening predisposes people to more energy storage; we simply don't expend
as much energy after an evening meal in comparison to morning meals.
Furthermore,
artificial light enables people to stay up later than they probably should and
often people don't get enough sleep. "If you stay up later, during a time
when you're hungrier for high-calorie foods, you're more likely to eat during
that time," Shea said. "You then store energy and get less sleep,
both of which contribute to weight gain."
"If
weight loss is a goal, it's probably better to eat your larger, higher-calorie
meals earlier in the day," said Shea. "Knowing how your body operates
will help you make better choices. Going to bed earlier, getting enough sleep
and choosing lower-calorie foods rather than higher-calorie foods in the
evening can all help with weight loss."
Conducted
by Shea and two Boston-area researchers, Frank Scheer, Ph.D. and Christopher
Morris, Ph.D. of Brigham and Women's Hospital and Harvard Medical School, the
study examined the appetite and food preference of 12 healthy non-obese adults
throughout a 13-day laboratory stay in very dim light in which all behaviors
were scheduled, including timing of meals and sleep.
Dr. Scheer, first author
on the study, explained that "by the end of this long protocol, all of the
participants' meals and activities were spaced evenly across the day and night,
allowing examination of the true internal circadian effects on appetite, while
controlling for other effects on appetite including the amount of food recently
consumed."
The
researchers found that the internal circadian system regulated hunger, with
participants feeling the least hungry in the morning (8 a.m.) and most hungry
in the evening (8 p.m.). Similar rhythms were found in appetite for types of
food, such as sweet, starchy and salty, and the estimate of how much food
participants could eat.
The study concludes that the internal circadian system
causes an evening peak in appetite that may promote larger, higher-calorie
meals before the fasting period necessitated by sleep.
"Our
study suggests that because of the internal circadian regulation of appetite,
we have a natural tendency to skip breakfast in favor of larger meals in the
evening. This pattern of food intake across the day is exactly what Sumo
wrestlers do to gain weight." said Steven Shea. "So, it seems likely
that the internal circadian system helps with efficient food storage. While
this may have been valuable throughout evolution, nowadays it is likely to
contribute to the national epidemic of obesity."
This
research was supported by NIH-R01-HL76409 and NIH-K24 HL076446 to SAS, NCRR
GCRC M01 RR02635; NIH-P30-HL101299 and NIHR01-HL094806 in support of FAJLS;
National Space Biomedical Research Institute through NASA NCC 9-58 in support
of CJM.
Story Source:
The
above story is reprinted from materials provided byOregon Health &
Science University.
Note: Materials may be edited for content and length. For further
information, please contact the source cited above.
Journal Reference:
1. Frank A.J.L. Scheer, Christopher J. Morris,
Steven A. Shea.The internal circadian clock increases hunger and appetite in
the evening independent of food intake and other behaviors. Obesity,
2013; 21 (3): 421 DOI:10.1002/oby.20351
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Oregon Health & Science University (2013, April 29). What
triggers those late-night snack cravings?. ScienceDaily. Retrieved
April 30, 2013, from http://www.sciencedaily.com/releases/2013/04/130430110321.htm
