When it comes to weight gain, when you eat might be at least
as important as what you eat.
When mice on a high-fat diet are restricted to eating for
eight hours per day, they eat just as much as those who can eat around the
clock, yet they are protected against obesity and other metabolic ills, the new
study shows. The discovery suggests that the health consequences of a poor diet
might result in part from a mismatch between our body clocks and our eating
schedules.
"Every organ has a clock," said lead author of the
study Satchidananda Panda of the Salk Institute for Biological Studies. That
means there are times that our livers, intestines, muscles, and other organs
will work at peak efficiency and other times when they are—more or
less—sleeping.
Those metabolic cycles are critical for processes from
cholesterol breakdown to glucose production, and they should be primed to turn
on when we eat and back off when we don't, or vice versa. When mice or people
eat frequently throughout the day and night, it can throw off those normal
metabolic cycles.
"When we eat randomly, those genes aren't on completely
or off completely," Panda said. The principle is just like it is with
sleep and waking, he explained. If we don't sleep well at night, we aren't
completely awake during the day, and we work less efficiently as a consequence.
To find out whether restricted feeding alone—without a
change in calorie intake—could prevent metabolic disease, Panda's team fed mice
either a standard or high-fat diet with one of two types of food access: ad lib
feeding or restricted access.
The time-restricted mice on a high-fat diet were protected
from the adverse effects of a high-fat diet and showed improvements in their
metabolic and physiological rhythms. They gained less weight and suffered less
liver damage. The mice also had lower levels of inflammation, among other benefits.
Panda says there is reason to think our eating patterns have
changed in recent years, as many people have greater access to food and reasons
to stay up into the night, even if just to watch TV. And when people are awake,
they tend to snack.
The findings suggest that restricted meal times might be an
underappreciated lifestyle change to help people keep off the pounds. At the
very least, the new evidence suggests that this is a factor in the obesity
epidemic that should be given more careful consideration.
"The focus has been on what people eat," Panda
said. "We don't collect data on when people eat."
