It turns out that when we eat may be as important as what we
eat.
Led by Satchidananda Panda, an associate professor in the
Regulatory Biology Laboratory, scientists at the Salk Institute for Biological
Studies have found that regular eating times and extending the daily fasting
period may override the adverse health effects of a high-fat diet and prevent
obesity, diabetes and liver disease in mice.
They fed two sets of mice, which shared the same genes,
gender and age, a diet comprising 60 percent of its calories from fat (like
eating potato chips and ice-cream for all your meals). One group of mice could
eat whenever they wanted, consuming half their food at night (mice are
primarily nocturnal) and nibbling throughout the rest of the day. The other
group was restricted to eating for only eight hours every night; in essence,
fasting for about 16 hours a day. Two control groups ate a standard diet
comprising about 13 percent of calories from fat under similar conditions.
Mice limited to
eating during an 8-hour period are healthier than mice that eat freely
throughout the day, regardless of the quality and content of their diet
After 100 days, the mice who ate fatty food frequently
throughout the day gained weight and developed high cholesterol, high blood
glucose, liver damage and diminished motor control, while the mice in the
time-restricted feeding group weighed 28 percent less and showed no adverse
health effects despite consuming the same amount of calories from the same
fatty food. Further, the time-restricted mice outperformed the ad lib eaters
and those on a normal diet when given an exercise test.
Their findings suggest that regular eating times and fasting
for a significant number of hours a day might be beneficial to our health.
Fasting Time
Important
"By eating in a time-restricted fashion, you can still
resist the damaging effects of a high-fat diet, and we did not find any adverse
effects of time-restricted eating when eating healthy food," says Megumi
Hatori, a postdoctoral researcher in Panda's laboratory and a first author of
the study. However, she cautioned that people should not jump to the conclusion
that eating lots of unhealthy food is alright as long as we fast. "What we
showed is under daily fasting the body can fight unhealthy food to a
significant extent," she says. "But there are bound to be
limits."
The Salk study suggests an option for preventing obesity by
preserving natural feeding rhythms without altering dietary intake.
The Salk study found the body stores fat while eating and
starts to burn fat and breakdown cholesterol into beneficial bile acids only
after a few hours of fasting. When eating frequently, the body continues to
make and store fat, ballooning fat cells and liver cells, which can result in
liver damage. Under such conditions the liver also continues to make glucose,
which raises blood sugar levels. Time-restricted feeding, on the other hand,
reduces production of free fat, glucose and cholesterol and makes better use of
them. It cuts down fat storage and turns on fat burning mechanisms when the
animals undergo daily fasting, thereby keeping the liver cells healthy and
reducing overall body fat.
The daily feeding-fasting cycle activates liver enzymes that
breakdown cholesterol into bile acids, spurring the metabolism of brown fat --
a type of "good fat" in our body that converts extra calories to
heat. Thus the body literally burns fat during fasting. The liver also shuts
down glucose production for several hours, which helps lower blood glucose. The
extra glucose that would have ended up in the blood -- high blood sugar is a
hallmark of diabetes -- is instead used to build molecules that repair damaged
cells and make new DNA. This helps prevent chronic inflammation, which has been
implicated in the development of a number of diseases, including heart disease,
cancer, stroke and Alzheimer's. Under the time-restricted feeding schedule
studied by Panda's lab, such low-grade inflammation was also reduced.
"Implicit in our findings," says Panda, "is
that the control of energy metabolism is a finely-tuned process that involves
an intricate network of signaling and genetic pathways, including nutrient
sensing mechanisms and the circadian system. Time-restricted feeding acts on these
interwoven networks and moves their state toward that of a normal feeding
rhythm."
Simple, Effective Lifestyle
Intervention
"The take-home message," says Panda, "is that
eating at regular times during the day and overnight fasting may prove to be
beneficial. If following a time-restricted eating schedule can prevent weight
gain by 10 to 20 percent, it will be a simple and effective lifestyle
intervention to contain the obesity epidemic.”
###
The
scientific findings has been published in Cell Metabolism which
focuses on reports of novel results in any area of metabolic biology, from
molecular and cellular biology to translational studies: Hatori M, Vollmers C, Zarrinpar A, DiTacchio
L, Bushong EA, Gill S, Leblanc M, Chaix A, Joens M, Fitzpatrick JAJ, Ellisman
MH, Panda S.
Time-Restricted Feeding without Reducing Caloric Intake
Prevents Metabolic Diseases in Mice Fed a High-Fat Diet.
Cell
Metab, 2012; DOI:
10.1016/j.cmet.2012.04.019
###
Footnote:
The National Health and Morbidity Survey in 2006 showed that
two out of every five adults or 43%, were either overweight or obese and an
alarming situation where the number of obese adults had more than tripled over
a decade, from 4% in 1996 to 14% in 2006.
Obesity increases the risk of a number of health conditions
including: high blood pressure, high cholesterol and type 2 diabetes. Lifestyle
modifications, including eating a healthy diet and daily exercise, are
first-line interventions in the fight against obesity.
See also “Malaysians getting obese - by eating too
heavily at night” by Florence A Samy in The Star, April 11, 2010
