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Is Your Metabolism to
Blame?
By
Ahmed H. Kissebah, M.D., Ph.D.
The term “metabolism” is
a word commonly used by almost every source
that deals with weight loss, obesity
research, and weight management. We also
receive a lot of inquiries from TOPS members
about the actual meaning of this word. There
are conflicting notions about whether our
metabolism is to blame or not in our
struggle to reduce our weight and then to
maintain the goal weight. How can we
understand and determine its impact on
weight gain and—at least, in some
individuals—its effects on maintaining our
weight goal? This article will address this
issue.
What is
metabolism?
If we compared your body to a car,
metabolism is everything that happens in the
engine when it is running. Human metabolism
is a set of biochemical events that keeps us
alive. Your metabolic rate is the rate at
which the body uses energy—expressed as
calories burned—over a given time. It
includes three categories:
1. Calories needed for
basic body functions such as breathing,
pumping of the heart, maintaining body
temperature, etc., is known as the Basal
Metabolic Rate (BMR). It accounts for
usually 50% to 60% of the calories expended
per day.
2. Calories needed for
the processes of eating, digestion,
absorption and maintaining body nutrients is
known as the Thermic Effect of Eating (TEE).
It utilizes between 10% and 15% of the
calories expended per day.
3. Calories used for
physical activities, called Activity Related
Energy (ARE), account for the rest of the
calories burned per day.
Thus, the metabolic rate
is adjusted to process what one eats, to
provide the power to move around and
exercise, and to maintain the energy
required for basic bodily functions.
Factors
Affecting the Metabolic Rate
What people need to know is how to
boost the metabolic rate so that a person
can burn more calories and, consequently,
control the process of weight gain. First,
BMR depends on age, gender, and body size
and composition, as well as the hormonal
balance. Women generally tend to have a
lower BMR than men, and older people tend to
have a lower BMR than younger people. This
is because the major burning organs in the
body are the muscles that, on a per unit
basis, burn more calories than the
relatively fatty organs and, thus, help to
boost the BMR. The metabolic rate is also
affected by climate. It is increased in hot
climates and sometimes also with the cold.
It is increased by fever and decreased by
fasting. It is also affected by our genes.
Thus, in order to increase the calorie
expenditure by increasing BMR, one has to
emphasize a build-up of the muscle mass.
This can occur with the
various forms of resistance exercise and
weight training. Choosing the type of
exercise is an important issue for the obese
individual. Pushing against the walls or
floor, lifting weights, or stretch exercises
are all very helpful in building up the
muscle mass in the upper body. The best
exercise for the lower body is leisurely
walking, which is also recommended for
people to control their weight after
reaching goal.
One important thing to
remember is that repeated bouts of weight
loss and regain, which is common among obese
individuals, can very seriously affect the
muscle mass. Every time a person loses
weight, the major component lost—at least in
the beginning—is muscle. When this person
regains weight, what is regained is
primarily fat and not muscle. Repeated bouts
of this behavior could eventually change the
composition of the body by decreasing the
overall muscle mass and increasing the fat
mass and, thereby, reducing the BMR.
Surprisingly, unconscious fidgeting or
moving around a lot is one of the best means
to having a higher metabolic rate. It takes
calories to fidget, so you may want to
become a fidgiter.
Basal Metabolic
Rate throughout Life and the Effects of
Hormones
Boys and girls, when examined at
age 5, have the same body composition, and
the relative fat to muscle mass is the same
for both sexes. At puberty, girls have an
increase in the relative fat to muscle mass
by about 10% to 15%. Whereas, boys will
maintain a lower fat percentage, they also
show an increase in their relative muscle
mass. This sex difference remains throughout
adulthood, but is made worse by pregnancy in
women and when men experience middle-age
crisis. In both cases, the ratio of fat to
muscle will tend to increase. Men will also
gain the majority of their fat in the
central part of the body. This type of fat
is highly active and has serious adversities
to health. Women, on the other hand, tend to
deposit the majority of their gained fat in
the thighs and hips. Though this fat is
mechanically harmful and may not be accepted
emotionally, it has a lesser impact on one’s
health.
These differences
throughout these phases are engineered by
the hormonal differences between men and
women. After age 40, there is a gradual
decline in the sex hormones in both men and
women. This results in a gradual decrease in
the muscle mass and an increase in the
relative fat mass, which is paralleled by a
gradual drop in the BMR. The total body
energy expenditure in general falls by about
10% to 15% between ages 40 to 70. This means
that the energy requirements with aging
become less and the goal of maintaining
weight requires a gradual reduction in
caloric intake. Hormonal replacement therapy
as well as certain diseases will also affect
the circulating hormonal levels.
Is Your
Metabolism to Blame?
Many people blame their obesity on
having a low BMR, but this is not all true.
Although a low BMR might make one
predisposed to weight gain, the BMR is
usually higher in the obese and overweight
people because they need more calories to
deal with their higher body weights.
We all know that
individuals who have lost weight to goal and
become KOPS have to consume fewer calories
than another person of the same weight
who has never gained or lost weight.
Thus, it is easier for a KOPS to gain the
weight back unless they keep consuming fewer
calories all their life. That is because
when they lost the weight, they not only
lost the fat but also a great deal of their
muscle mass. Their body composition is
essentially the same as an obese person,
except they are thinner. That person will
require the gain of muscle mass by doing
those resistance exercises as described
earlier.
Although promoters of
certain diets would say that consuming
exclusively protein-rich diets could boost
your metabolic rate and weight loss, this is
not true. The process of weight loss and
maintenance is only determined by how many
calories the person eats and how many
calories are being expended. It is true that
it takes the body a little more energy to
process proteins than other nutrients.
However, eating more protein has only a very
small effect on the BMR. Other factors that
are expected to increase metabolic rate are
eating frequent, small meals; consuming
green tea supplements; and getting enough
sleep. Green tea extract is often promoted
as a weight-loss aid and might, in theory,
help. It contains certain “vital chemicals,”
including caffeine, that can briefly
increase BMR, although the increase is
small. Inadequate sleep has also been linked
with weight gain and, possibly, reduced BMR.
Although it is not easy
or even possible to boost the BMR, it is
much easier to increase the activity-related
energy expenditure simply by exercising
more. The calories one can burn during a
workout can be highly important in losing
weight and maintaining that weight loss.
Aerobic exercise such as running, biking,
swimming or brisk walking can help to burn a
significant portion of the daily calories
expended. Thus, there should be a balance
between the time spent in resistance
training (which affects the body’s muscle
mass and BMR) and aerobic exercise (that
helps to boost the calories spent by
physical activities). A balanced workout
should include both activities. However, one
has to be realistic and consider the fact
that many overweight individuals have joint
and tendon problems, back issues and even
heart disease. The activities selected for
these individuals have to take into account
their physical limitations. These
individuals should consult with their
personal physician and also with a
specialist in exercise training.
Therefore, is the
metabolic rate to blame? The evidence does
not support this claim. It is up to the
individual to adopt a lifestyle behavior to
positively affect the body’s composition
and, consequently, the BMR as well as their
activity level, which also impacts their
caloric expenditure.
Who Should We
Blame?
First and foremost, are your genes.
The metabolic rate like most body functions
is under the control of our inherited
network of genes. There are those
individuals who can consume a larger number
of calories than you, yet remain slim
throughout life. Their metabolic rate is set
at a higher level. Other people eat much
lesser amounts of food and yet can easily
gain weight. This is an area of research
that hopefully will disclose soon some means
to readjust these differences.
Second, one should be
aware of the various factors that affect the
body’s metabolism throughout her/his life
and utilize this knowledge to offset the
unwanted effects of pregnancy in women,
middle-age crisis in men, and aging in both.
One can always, however, increase their
metabolic rate by adopting lifestyle
behaviors that serve to maintain the muscle
mass and the body’s composition at a
favorable state. This will sustain a higher
basal and activity related metabolic rate.
As a TOPS member, these tools are already in
your hands. You can do it!
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