Weight management Capter 9-1
Lecture notes by professor Betty Cohen as recorded by Michal Domeny
When we are talking about weight management, it is crucial that we discus the
physiological aspects of weight management. Reason for that is that understanding
how our body respond to weight loss, will help us to ward off sliding into the
popular gimmicks about weight loss, presented to us in numerous weight loss books
and magazines.
Before we engage into this discussion, we need to define one word that is
indispensably associated with wt loss. This word is a diet. What diet really means
is, a way of eating. And healthy diet, is a diet that doesn’t put patient into risk for
any disease. This is what we will be discussing here.
Another thing we need to talk about, is counseling. One of the most important
thing we need to get our patients to understand, is that weight loss, is not something
that will happen over the course of the night. It really takes period of time, and we
shouldn’t judge the effectiveness of weight loss program based on the speed with
which we achieve it.
Patients really have to understand that diet is not merely physical change, but also
physiological. The main success of diet should be judged based on internal changes,
not external, as many people do. And so in this light, we should look for changes in
percentage of adipose tissue, and lean muscle mass, instead of just- did the patient
lost or gained weight? What you are then really interested in is, whether or not they
reduced their risk for chronic disease through following this diet.
Here we started talking about some of the health risks associated with excessive
weight. What are they:- diabetes -type II(NIDDM)
- MODY- mature onset diabetes mellitus seen in
children
- hypertension that can lead to stroke
- atherosclerosis
- increased level of saturated fats that increase LDL
- there is relation to different types of cancers
Besides these main areas, there are other areas where obesity is a risk factor
They include - Gallbladder disease
- Hiatus Hernia
Saying all the above, when you are talking to the patient, try to explain them,
that by following this diet, they will feel much better, they will look better, and they
will be around longer.
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Physiology
Majority of energy we consume, goes towards our BMR. The basic principle of
reduction diet is that, if you eat more kcal than your body needs, you will gain on
wt. If you eat less then what your body needs, you will loose wt. We know from
normal nutrition, that our BMR will decrease by 10% every decade after we reach
the age of 30. This may cause us to gain on some weight if we continue eating the
same amount of kcal as we used to do in our 20's . The major reason however, why
people in their middle age put on weight is, that they loose their lean muscle mass.
If you remember from normal nutrition, one of the major things that determines our
BMR is the proportion of lean muscle mass in our body. It is the lean muscle mass,
that contain the most mitochondria (our power house) that creates our energy. For
the same reason, man whose bodies contain more lean muscle mass, have higher
BMR.
Another factor that comes to play when we are determining our total kcal need is
AF- activity factor. And this is a big issue in our society, where majority of people
are not moving, and are sedentary. This factor comprises roughly 20-40% of our
energy need. It will be 50% only for professional athlete that excise vigorously
every day.
And the last factor is TEF- thermic effect of food, which is about 5-10% of our
Kcal need. These are then the three main factors determining our total energy need.
One of the problems with weight is the fact, that after you loose wt initially, you
stop losing weight after a while. This however , doesn’t make sense in the light of
what we know about wt loss. We said that to loose 1 lb of fat we need to cut back
on 500 kcal a day, which will create deficit of 3500kcal in a week, which is what 1
lb of fat is equal to. According to this statement then , it should be clear that if you
create deficit of 3500 kcal, you should loose 1 lb of fat. The reason though, why
we stop losing wt, is related to what increases and what decreases our BMR.
First thing is the percentage of lean muscle mass on our body. For man the
percentage of fat is between 12-18%, for woman 20-24%.. If you have lower % of
fat in either sex, it will reflect on your reproductive system. For example, if man
athlete has % of body fat around 3%, he will loose ability to impregnate women- he
will become impotent. If on the other hand, women has very low % of body fat,
lower then 10%, as we can see in some young female athletes, they will have later
onset of puberty, and they will not be menstruating. The reason for that is, that if
your own body is lacking what it needs to stay healthy, it doesn’t have anything
extra to give out -for reproduction. For that reason, we can see that lower body fat
content, below what is recommended, is not necessarily healthier.
For interest might be that one of the reasons why female athletes are trying to
delay onset of menstruation is the fact, that with onset of menstruation come hand
in hand internal changes in fat metabolism , that will have result in automatic 4 %
increase in body fat content to provide for possible pregnancy
Extra material
There was a question today in the class, if obesity has anything to do with
menstrual cycle. The answer is yes. First influence can be observed in young girls
where due to the general increase in obesity, we can see significant drop in the age
of onset of Menarche - first menstruation. At this time the border is moving close
to 10 years of age.
The second influence of obesity on menstruation is regarding the strength and
length of menstruation. In women that have lots of adipose cells, these cells are
responsible for producing too much estrogen. This then leads to increase in
menstruation. The usual treatment of choice is progesterone shots, to normalize this
hormonal imbalance.
What are the other factors that influence BMR.
As we said the major ones are lean muscle mass that increases BMR. On the
other hand abundance of fat decreases BMR, because it replaces muscle mass. The
fact that fat cells contain only 25% of the lean muscle cells mitochondria content,
explain why obese people have harder time to burn fat.
-Fewer is another factor that increases BMR
- Cigaret smoking and nicotine. In normal weight people, it will increase BMR
by 1-2 %. If they stop smoking, this 1-2% can play a role in gaining weight. The
major reason however why people who stop smoking gain weight is, because when
they were hungry, they started smoking cigaret. Now they lost this “toy:”, and they
replace it with food, which will contribute extra kcal.
Another thing that influence BMR is reduced Kcal intake. Once you decrease
your intake of food ,your body will switch into self preserving mode, that will
reduce the amount of kcal burned in order to preserve energy. This is basic survival
mechanism that helped our ancestors to withstand periods of time with limited food
supply. This is however mechanism that stays in way of many people towards
successful weight loss. . In order to prevent this drop in BMR, you should never put
anybody on reduction diet that is lower in kcal than his BMR. For most people this
represents approximately 1600Kcal. Unless you are 4'10" - 5"- where you can go up
to 1440 kcal.
In order to develop a diet, that will help your patient to loose weight, first
calculate his total kcal need. You can use this easy formula
Women=0.9 kcal/kg/hour =21.6kcal/kg
Man =1kcal/kg/hour =24kcal/kg
After that you will multiply this number by his activity factor. The question
remains what weight are you going to use to calculate his Kcal ? You can use either
his adjusted wt, or reasonable weight that he wants to be at. It doesn’t have to be
necessarily his ideal body wt.
Next thing is to change this patient’s activity level. Not all of us may have time
to go to gym on regular basis , and not all of us can afford it either. That’s why we
need to look into ways of incorporating exercise into our daily routine. In the class
we talked about walking. Walking 1 mile burns approximately 100kcal. If you will
run this mile, you will be able to do this in a shorter period of time, which will
allow you to run more than 1 mile. If you can walk 5 miles ,or burn 500 kcal a day -
every day- you will loose 1 lb in a week.
Once again remember that you should never put nobody on diet that is lower than
his BMR. Some say that you can go as low as 1200kcal, but this is a border line
below which it is well known, that you cannot provide your body with sufficient
nutrients. Moreover, at this low kcal intake, you will decrease your BMR that will
lead in drop, and eventual loss of progress towards weight loss. And don’t forget
also the fact that patient on such a low kcal diet. will be probably very hungry, and
thus his level of compliance will most likely eventually fade, and he will drop out of
the program.
At the end of today’s lecture, we will mentione briefly that in our body we have 2
types of fat cells.
-the white adipose tissue that we try to curb as much as possible
- brown adipose tissue. This tissue is most abundant in new born baby who lack the
sufficient surface area to produce enough heat to keep constant internal body
temperature. This tissue then burn lots of kcal because it has high content of
mitochondria. Unfortunately we loose most of this tissue after first year of life.
There are however individuals who keep their large % of brown cells and they will
have generally problems with gaining weight .
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