Most religions use periods of fasting as a means of
demonstrating faith or penitence, and an opportunity for spiritual reflection.
Fasting has also historically been a means to express political views and a
form of protest.
Though it may not be the most practical -- or
safest -- diet, some people use fasting as a way to lose weight or to cleanse
the body of toxins, although some experts say our bodies are perfectly equipped
with organs that already do the job. How fasting is used for weight loss varies
by diet. Some fasting diets involve drinking nothing but water or eating only
raw foods for a period of one or more days, while others restrict food on
alternate days. Certain fasting diets only allow liquids like water, juice, or
tea, while others dramatically cut calories but do not eliminate food
altogether.
Does Fasting Help
You Lose Weight?
When you fast, your body is forced to dip into
energy stores to get the fuel it needs to keep going, so you will lose weight fasting.
The big question is how long you will keep that weight off. Because food was
often scarce for our ancestors, our bodies have been genetically programmed to
combat the effects of fasting. When you eat less food, your metabolism slows
down to conserve energy. Then, when you go back to your usual diet, your
lowered metabolism may cause you to store more energy, meaning that you will
probably gain back the weight you lost and possibly even put on more weight
when eating the same calories you did before the fast.
As you fast, your body will adjust by reducing your
appetite, so you will initially feel less hungry. But once you have stopped
fasting, your appetite hormones will kick back into gear and you may actually
feel hungrier and be more likely to binge.
Research has shown that fasting on alternate days
can help people lose weight, but not for long. In one study, people who
followed an alternate-day fasting diet shed weight, even when they ate all they
wanted on the nonfasting days. However, they could not maintain the weight loss
over time.
Can Fasting
Detoxify the Body?
Some fasting diets claim that they can cleanse the
body of impurities. However, there is no evidence that fasting detoxifies your
body, or that your body even needs to be detoxified. It is naturally designed
to remove toxins through the skin (by sweating), liver, colon, and kidneys.
Could Fasting Help
You Live Longer?
Studies of fasting in both rodents and humans
appear to indicate a connection between calorie restriction and longevity. In
one study of overweight men and women, a calorie-restricted diet improved
markers of aging, such as insulin level and body temperature.
Fasting might also improve longevity by delaying
the onset of age-related diseases including Alzheimer's, heart disease, and
diabetes. One study showed that skipping meals once a month, as members of the
Mormon religious group do, reduces the risk of clogged arteries (the build-up
of plaque that can lead to heart attacks and strokes). However, it is not clear
from this research whether fasting alone or the Mormons' generally healthier
lifestyle (they also abstain from coffee, alcohol, and smoking) is responsible
for the improved heart health.
Researchers do not yet know whether the effects of
fasting translate into an actual increase in lifespan, because they have not
followed people for long enough periods of time. However the concept of
intermittent fasting, such as skipping a meal purposefully on an intermittent
basis, is gaining attention. It appears to be a relatively safe way to reduce
caloric intake that is easier for some people to do. The data however is not
there yet nor is this an accepted practice.
Is Fasting Safe?
Fasting for a day or two probably won't hurt people
who are generally healthy, provided they maintain an adequate fluid intake.
However, fasting entirely for long periods of time can be harmful. Your
body needs a variety of vitamins, minerals, and other nutrients from food to
stay healthy. Not getting enough of these nutrients during fasting diets
can lead to symptoms such as fatigue, dizziness, constipation, dehydration,
gallstones, and cold intolerance. It is possible to die if you fast too long.
Even short-term fasting is not recommended for
people with type I diabetes, because it can lead to dangerous dips and spikes
in blood sugar. Women who are pregnant or breastfeeding, or anyone with a
chronic disease, should not fast.
Before you go on any type of new diet, particularly
one that involves fasting, talk to your doctor to find out whether it is safe
and appropriate for you. Also ask your doctor to refer you to a registered
dietitian, who can show you how to design a healthy eating plan.
