Researchers Say When You Eat Each Day May Be Crucial
to Weight Loss
Mice on Time-Restricted Diets Had
Lower Cholesterol, More Muscle Than Unrestricted Mice
By Angela Chen in the Wall Street Journal
Most diet advice focuses on calories
and nutrients, but new research suggests that when you eat may be just as
important.
That’s one conclusion of a new study
by Dr. Satchidananda Panda, an associate professor at the Salk Institute for
Biological Studies, in La Jolla, Calif. Mice that were forced to limit how many
hours they ate were thinner than mice that chowed down whenever they wanted,
Dr. Panda’s team found. This was true no matter what kind of unhealthy diet the
mice ate.
The finding suggests scheduling may
play a critical role in losing weight, according to Dr. Panda. Mice on the
“time-restricted feeding” diet also had better muscle mass and lower
cholesterol, even though they were allowed to “cheat” and eat normally on the
weekends, Dr. Panda added.
Such findings support the rising
popularity of fasting diets. The 2012 best seller “The 8-Hour Diet” was based
in part on Dr. Panda’s work, while the so-called 5:2 Diet—eat how you like for
five days, fast for two—draws from similar research.
“I started researching the book in
2011 because of the work done on the benefits of intermittent fasting,” says
David Zinczenko, co-author of the “The 8-Hour Diet.” He says he decided to
create a time-restricted plan because he found intermittent fasting, which
involves fasting for days at a time, to be unrealistic. For the book, Mr.
Zinczenko put about 150 volunteers on the diet. The majority self-reported that
they lost weight.
Christopher Ochner, a director of
research development at Mount Sinai Hospital who focuses on obesity, warns that
studies of time-restricted feeding may be the latest in a long line of mice
studies that don’t translate to people. He says the old idea of “calories in,
calories out” matters more for health than how many hours someone eats, or what
time of day they are eating.
If time-restricted feeding worked in
humans, people who skip breakfast and then eat a late dinner would be much
thinner than everyone else, Dr. Ochner says. Observation shows this isn’t true,
and study results are “very mixed” regarding whether skipping breakfast causes
weight loss, Dr. Ochner says.
In the latest paper Dr. Panda worked
on, published in December in the journal Cell Metabolism, his team put obese
mice on a variety of unhealthy eating regimens, including high-fat and
high-fructose diets. One set of mice ate at all times, while another set ate
only during periods of nine, 10, 12 or 15 hours. Both sets were given the same
unhealthy food options, and both sets ate all the food available, according to
the research.
Because the restricted mice could
still eat as frequently as they wanted within the given time frame, none of the
research tracked the effects of large meals versus smaller, or of frequent
snacking.
The benefits of restricted eating
times were proportional to the amount of time fasted, said Amandine Chaix, a
Salk researcher who works with Dr. Panda. The narrower the window for eating,
the more weight the mice lost.
Researchers have found that
time-restricted diets such as eating for only eight hours a day can lead to
weight loss. Dr. Satchidananda Panda discusses his research with Sara Murray.
Photo: iStock/monkeybusinessimages.
The researchers think this is partly
because the restricted schedule aligns with the body’s circadian rhythm, or
internal clock. Eating happens at times when the body is more efficient at
breaking down foods.
“The metabolic system evolved to be
able to allocate energy resources at different times of the day,” said Dr.
Chaix. Cholesterol is broken down in the body by bile acids, which are
controlled by an enzyme that is most present upon wakening. The mice started
eating soon after they got up, which helped their bodies break down cholesterol
more efficiently. In addition, when mice eat randomly, their livers cannot
switch off the glucose production process. This leads to high blood sugar levels,
which damages the body.
For humans, eating during the day
may be beneficial because it’s been the pattern for millions of years, says Dr.
Panda. The rise of eating later at night might have thrown off the circadian
rhythms that evolved in humans, and might have contributed to the rise of
obesity, he added.
In a previous study, his team found
that mice who tended to eat high-fat diets at off times, spreading their
calorie intake equally between day and night, were more likely to grow obese.
But when they were forced to eat when they were most awake and active, this
effect disappeared.
A second benefit comes from fasting
itself, says Mark Mattson, chief of the Cellular and Molecular Neurosciences
Section at the National Institutes of Health. After fasting, the body starts to
use fat, instead of glucose, as a source of energy. This leads to faster weight
loss, among other benefits, he explained.
Dr. Mattson believes that the
three-meal-a-day diet is abnormal from an evolutionary perspective and that periodically
going without food strengthens the body. His studies have found that mice
forced to fast are thinner and have lower levels of insulin and glucose,
meaning they are at lower risk for developing diabetes.
“We think that one of the reasons
fasting is good for the body and brain is that it imposes a mild stress on
cells,” he says. “The cells then adapt to improve an ability to cope with more
severe stress and we think to resist diseases and aging.”
Another of his studies on mice
suggests that fasting protects against stroke and slows cognitive decline. He
is now starting a study in humans, focusing on whether fasting protects the
brain from Alzheimer’s disease.
Krista Varady, an associate
professor of nutrition at the University of Illinois in Chicago and author of
“The Every-Other-Day Diet,” has found that people fasting every other day can
lose up to 30 pounds in eight weeks, which is far more than those on a more
typical calorie-restriction diet.
Poster’s comments:
1)
This
article is written for good times.
2)
All
things in moderation (many mothers would say so) is another consideration.
3)
Diet
and exercise do go together for so many of us.
4)
During
hard times we often get enough exercise anyway.
5)
I
agree with the idea that we are what we eat.
6)
Simple
daily tasks, like cleaning a house or walking around work do provide some
exercise value that should be counted in some way, too. It all adds up.
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