Lancaster Physician Fall 2019 - 27

FA L L 2 0 1 9

T

he method of intermittent fasting
as a weight loss strategy has stirred
debate within the health nutrition
realm, especially given the limited
evidence to support its widespread use.
Much of the science supporting intermittent fasting has come from animal studies,
where for instance, reductions in insulin
resistance, cardiovascular, and inflammatory
markers were demonstrated in obese rats on
time-restricted diets. However, the majority
of human research finds intermittent fasting
to be no more effective than conventional
diets. One meta-analysis (Harris et al. JBI
Data Sys Rev 2018) reviewed six studies
and concluded that intermittent fasting
was more effective than control but is not
superior to caloric restriction in losing
weight. Cioffi et al (J Transl Med 2018)
reviewed eleven trials and reached the
same conclusion. A 2019 crossover study
(Ravussin et al. Obesity 2019) concluded
that although time-restricted eating may
increase fat oxidation, weight loss was
facilitated through decreasing appetite
rather than by increasing energy expenditure. This study, limited by small sample
size (11 patients) and short duration (four
days), looked at the mechanisms behind
intermittent fasting rather than the actual
outcome of weight loss.

INTERMITTENT
FASTING IS NOT
RECOMMENDED
FOR:
* Pregnant or breastfeeding
women
* Anyone with history of an
eating disorder, or
otherwise unhealthy
relationship with food
* Diabetics
* Patients who experience
low blood sugar
* Women who are trying
to conceive
* Children and the elderly

While lacking evidence that intermittent
fasting works better than conventional diets,
the momentum behind this movement
comes largely from public figures and social
media influencers, rather than researchers
and health professionals. This phenomenon
brings challenges to the clinician when a
patient asks for an "expert" opinion about
intermittent fasting as a weight loss option.

daily caloric intake by 60-80 percent. This
is followed by a "feeding day" that has no
limits on food intake. Other variations are
often described by ratios: for example, 5:2
intermittent fasting is based on five days of
normal eating and two days of restriction.
Another type of time-restricted feeding is
based on the 24-hour day, with 16 hours of
fasting and eight hours of eating (known as
the 16:8 method), for example. Supporters
of intermittent fasting tout its simplicity,
in that tracking calories or eating specific
foods isn't necessary; simply eat "ad libitum"
during the proper time, and the weight
will come off.

What is Intermitent Fasting?
Intermittent fasting is not an actual diet,
but instead describes an eating pattern
based on time restriction rather than food
restriction. In a broad sense, intermittent
fasting is the practice of scheduling routine
times for eating and fasting, either setting
them over the course of the day, or spreading these times over the week. One version
of intermittent fasting involves a "fasting
day," when food intake is either completely
restricted or significantly reduced, limiting

The theory behind intermittent fasting is
based on metabolic differences that occur
between times of "fasting" versus "feasting."
Readily available energy comes from our
food while "feasting," where carbohydrates
are broken down into sugar as an energy
source. Between periods of "feasting" (i.e.,
fasting), our cells switch from using glucose
as the primary fuel source to relying on fat
stores for energy. In other words, the body
burns fat instead of sugar during times of
fasting. Fatty acids known as ketones are

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PHYSICIAN

released into the bloodstream when fat
is burned; however, intermittent fasting
alone does not generate sufficient ketosis
for effective weight loss.
Risks of Intermitent Fasting
It all sounds simple and logical, but
there are risks to intermittent fasting. The
primary dangers are hypoglycemia and
dehydration, both of which can occur
during long periods of fasting. Other risks
include nutritional deficiencies, tiredness,
irritability, altered metabolism, and the
general unproven nature of this behavior.
Fasting could adversely affect ovulation
and fertility in women and may lead to
menstrual disorders.
Additionally, there is the obvious risk
of unsustainability, where individuals are
not able to keep to the prolonged fasting
schedule. Maintaining periods of fasting
in daily life becomes challenging because
of social obligations, cravings, stress, and
otherwise busy schedules. Despite our best
intentions, life can get in the way of keeping
to a fasting schedule. Unfortunately, like
many weight loss strategies, returning to
old habits often leads to weight recidivism.
Intermitent Fasting and Bariatric
Surgery
Bariatric surgery is a recognized treatment of morbid, or clinically severe,
obesity. When combined with a comprehensive treatment plan, bariatric surgery
can be an effective tool to provide longterm weight loss and better quality of
life. Bariatric surgery has been shown to
improve or resolve many obesity-related
comorbidities, including type 2 diabetes,
hypertension, heart disease, sleep apnea,
and more. Many surgical patients find
themselves taking less medications to treat
these obesity related diseases.
Bariatric operations, such as the gastric
bypass and sleeve gastrectomy, work by
changing the anatomy of the gastrointestinal
tract (stomach and digestive system) or by
changing the physiology of energy balance
Continued on page 28
Lancaster Physician Fall 2019

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