Talk of intermittent fasting is making the
rounds as a way to lose weight and stave off
or alleviate chronic disease, but is it right for
everyone or just a fad?
We’ve asked Calvert Internal Medicine Group
Endocrinologist Dr. Julie O’Keefe to help
readers understand what intermittent fasting
is, who can benefit from it and why it can
be effective.
“Losing weight in theory is very simple, but in
practice is very difficult,” said Dr. O’Keefe.
“Time-restricted eating is a strategy that
designates periods of eating and periods of
fasting. The periods of eating and fasting can
vary but they have in common a period of time
when there is no food consumption—usually
eight or more hours.”
Availability of Food
The ability of humans to go without food for long
periods of time is built into our body systems.
Primitive people had to hunt, they had to gather,
and they had to prepare and store food. Food was
not available to consume 24/7.
Our bodies can go without food for several
hours, for several days, and even longer because
our bodies are developed to store fat. In other
words, human bodies are equipped to encounter
periods of fasting.
Humans evolved to be in sync with the
day/night cycle, or a circadian rhythm. Our
metabolism has adapted to daytime food and
nighttime sleep. But what if due to technological
advances, humans have the option to be alert and
active during the night and have access to food at
all hours?
How Human Bodies Process Food
Our bodies need nutrients from food and drink
in order to work properly and keep us healthy.
Proteins, fats, carbohydrates, vitamins, minerals
and water are nutrients. The digestive system
breaks these nutrients down into parts small
enough for our bodies to absorb and use for
energy, growth and cell repair.
The digestive process starts with the first
bite of food but can take up to eight hours
for food to pass through the stomach to the
small intestine.
“Intermittent fasting designates a period
of time, usually greater than eight hours,
during which we do not take in calories,” said
Dr. O’Keefe. “This fasting state allows our
body time to process the nutrients we have
eaten and to burn fat.”
Timing of Meals
There are two schedules of intermittent
fasting that most people follow. The most
common is the daily 16-hour-no-food/8-
hour-food schedule. This means that if you
normally eat your first meal at 8 a.m., you
have your last meal eight hours later, at
4 p.m. You can change the time of consuming
food according to a schedule that works best
for you. So, if your family eats dinner at 6 p.m.,
then you adjust and don’t eat breakfast until
10 a.m. The idea is that you eat only during
an 8-hour time period—and that’s it. No
more food or snacking outside of that time
period. You can drink water, but ideally you
are not putting any calories in your body
during that 16-hour time period of fasting.
Another intermittent fasting schedule
is more restrictive. The 5-2 schedule follows
that for five days out of the week you eat
when you want and then two days out of
the week you are just eating one meal a
day, consisting from 500-600 calories and
drinking water or black coffee for the
remainder of the day.
Benefits of Intermittent Fasting
According to the National Institutes of Health
(NIH), the majority of available research
shows that intermittent fasting is effective
at reducing body weight, decreasing fasting
glucose, decreasing fasting insulin and
reducing insulin resistance, which is the
precursor of Type 2 Diabetes.
Just changing the timing of meals,
by eating earlier in the day and extending
the overnight fast, significantly benefited
metabolism even in people who didn’t
lose weight.
Is Intermittent Fasting
Right for Me?
As with starting any new diet or
health regimen, people should
consult their primary care doctor to
ensure that intermittent fasting is
safe for them.
“Adherence is a major factor
in the success of any dietary
intervention,” Dr. O’Keefe said.
“Patients need to choose a dietary
regimen that will work in their
lifestyle. If someone is interested in
intermittent fasting, I explain the
process and let them decide what
would work best for them.”
Foods Included in
Intermittent
Fasting Program
“There are no specific food
restrictions with intermittent
fasting. However, all prescribed
diet programs should emphasize
the intake of as many unprocessed
foods as possible: fresh vegetables,
lean meats and fruits. Though you
may be following a restricted time
period to eat, if you spend the time
eating take-out and junk food, you
will not have successful weight
loss.” said Dr. O’Keefe.