Eat Late, Put on Weight?
Study Shows Eating at the 'Wrong' Time of Day Could Lead to Weight Gain
WebMD News Archive
Sept. 3, 2009 -- Excessive late-night eating has long had a bad reputation,
with studies showing it leads to weight
Now, in a new study, researchers from Northwestern University have found
that eating at the "wrong" time leads to more than twice as much weight gain, even when the
overall calories consumed are the same as those eaten at appropriate times.
Their research is confined to animals, but the results are dramatic enough
to point to the need for more human research, says Deanna Arble, a PhD student
at Northwestern and the study's lead author.
''We've found that mice who are allowed to eat during the light phase --
their 'wrong' time of day -- gain substantially more weight than those allowed
to eat during the dark phase, the right time of day for them to eat," she tells
WebMD. The study is published online in the journal Obesity.
Based on the research, however, it's not possible, Arble says, to set an
optimal time window for people to eat to maintain weight. Rather, she hopes the
finding will be a trigger for obesity scientists who study people to focus more
closely on the concept of the timing of eating.
In the study, Arble and her colleagues gave two groups of mice, who are
nocturnal and expected to eat at night, the same high-fat diet. They gave one
group access to food at night and the other group access during the day. Both
groups could eat as much as they wanted during the 12-hour feeding phase.
'Right' Time vs. 'Wrong' Time
At the end of the six-week study, the mice who were fed during the light
phase -- their ''wrong'' time to eat -- gained much more weight than those fed
during the dark phase.
When the researchers compared the animals' weight at the study start to
their weight at the end, the mice that ate at the wrong time had a 48% weight
increase, while those who ate at the correct time had a 20% weight
While both groups gained, Arble notes, the mice that ate at the wrong time
gained more than twice as much weight. "We did not restrict the amount of
calories they were eating," she says. Even so, between groups, ''there was no
difference in the [average] amount of calories consumed."
The only variable, she says, was when the food was consumed.
Arble can't say for sure why the mice that ate at the ''wrong'' time gained
so much more weight. ''We speculate that it's the interplay between body
temperature, metabolic hormones such as leptin, and the sleep-wake cycle," she
For humans, nighttime is a time for rest, as the body temperature declines,
she says. "Eating at night is contradicting your body's natural circadian
rhythm,'' she says. "The leptin levels are starting to rise, and are supposed
to be discouraging you from eating." Rising leptin levels suppress