Lecture notes by professor Betty Cohen as recorded by Michal Domeny
(These lecture notes have been adapted almost autentically from tape recording
made during this lecture )
Weight loss continuing 5.2.2001
Before we begin, let’s clarify few terms
There is a difference between being over weight , obese and being morbidly
obese. It has to do with what % of acceptable body weight somebody is . An over-
weight person is less then 20% over “IBW”= acceptable BW. Obese is more than
20% , and morbidly obese is more than 100% IBW.
We talked about BMI . The risk for disease is BMI more than 27, and the doctor
would classify you as obese if your BMI was more than 27. Because of different
body types, apple or pear shape, we also look at waist to hip measurement. Obesity,
and higher health risk, is when you have in women, waist to hip ratio =0 .8, and
for man w/h measurement over 1.0 So you would measure you waist, and divide it
by your hip measure.
It has also been found that health risk will go up for women, when their waist
circumference is over 35, and in man over 40 inches. This also describes obesity.
Remember that BMI is not used for high performance athletes such as NBA
players. When we are talking about health risk, we need to keep in mind what
health risk stands for. Health risk means that it increases your chances for getting
disease It doesn’t mean that you will get the disease, but that there are many
different risk factors and this is one particular risk factor (BMI)
When we look at weight measurement, there are all sort of aspect to why
someone is over weight , under weight, or have never had problem with wt. And
one of the things we might look at, is heredity. But besides heredity you also have
environmental and developmental factors. And so there was a time, when people
said it would be either one, or the other . Now it is very easy to say that all those
things are related, and you can't have one without the other. And so if we look at the
history of obesity research, we can see that in 1965 the fat cell theory was
developed. In about mid 80's set point theory was developed.. And in 19994 in
Rockefeller university, one of the researchers discovered the obesity gene. In
finding obesity gene, he found that there was a protein that was produced by this
obesity gene called leptin. Leptin in Greek lep -= thin ( gene that makes you thin.
Lets just go back a little bit and start with heredity
If you look at twins, mostly you will se that they stay the same, and weigh as
one another. In studies that used to be done throughout the 60's, they looked at
families with identical twins, families with non-identical twins, and all different
kind of combinations. Basically what they found was that
- if 2 birth parents were obese, there was a minimum of 80% chance that the children
would be obese
- if one parent was obese, there was 60% chance
- if no parent was obese, there was a chance less than 10% that the child would be
obese.
Now you can say that it is genetic, or it is because the way our parents feed us.
Of course you can also say that it might be later on, during school period, that we
get inspired in our eating habits by others -your peers.But basically what they
found was that there is a relationship between parents and obesity, and basically it
has to do with the 1994 discovery of the obese gene .
Leptin is a protein, that this gene controls the synthesis of, and just like every other protein in the body, it has to get across the cell membrane . To do that, there has
to be receptor sites on the cell membrane . Receptor sites are always made out of
protein, so there is receptor protein, and protein itself -leptin . And so what they
found out was that when leptin gets across the cell membrane into specific-feeding center
of brain, it will make you feel full . But what they found was that even though leptin
injected to mouse caused them to starve to death, when they injected people with leptin,
nothing happened. The reason for that is that there has to be receptor for the leptin,
not just the leptin itself. So similarly as in people with diabetes, in whom receptors for insulin are not as effective as in healthy individuals , in some people these receptors for leptin are not function optimally either. So even though they are making leptin, their receptor sites are not working for one reason or another, and the body
doesn’t recognize the leptin The result is that the person keeps on eating and doesn’t
feel satiated.
But again, there is never one trigger for appetite. What they have found was that if
somebody loses weight, leptin levels decrease So we can see that there is some
kind of mechanism that signals body to stop producing leptin when we loose
weight. Consequently your body feels hungry, and you want to eat because your
body perceives it as all of sudden “I am starving” .We will see how all this goes
back to set point theory, and fat cell theory. So what has happened over the years is
that there was greater understanding of the fat cell theory, and set point theory.
There is another protein produced in the body, and it is called G-L-1. It is a
protein that is necessary for the absorption of nutrients out of the small intestine .
It slows the digestion of food, so that the nutrients can be better absorbed.. G-L-1 is
produced by cells in the small intestine. One of the way G-L-1 works is by slowing
digestion so that nutrients can be better absorbed in the small intestine. When they
were looking at people who were over- weight or underweight, however, they found out
that it also suppresses appetite. So when this is secreted, you don’t have
much appetite. But now they are saying- is its function only to make you feel full,
or is it a reaction of having food to stay in digestive tract. So again it is not just
one thing. -to make for example synthetic leptin. That is not gona work, because then
they would have to make synthetic G-L-1, and then they would have to make
synthetic receptors and other things involved here. Eventually with genetic
engineering, they will probably be able to make sure that the chromosome is
producing enough leptin, but right now we don’t have that kind of genetic
engineering ,and we may want to wander whether we want that kind of generic
engineering .
The area of the brain , that controls your appetite is located in Hypothalamus. It
controls the so called adaptive thermogenesis. It controls body ability to use fat for
energy. And if the body doesn’t use fat for energy that it stores fat in fat cells. That
leads us to the fat cell theory
Fat cell theory
The fat cell theory says that we are born with a certain number of fat cells It says
that there are certain people that are born with few fat cell that’s about 20-30 billion
of fat cells. Then there are certain people who are born with larger number of fat
cell, that’s about 50- 100 billion of fat cell. And then there are people born with
200 billion fat cells. And there was found that people who are born with the 20
billion fat cells tend to always be thin their entire life, or more precisely, that they
will maintain their weight, and will be at normal weight . People with less than 20
billion, are generally never able to gain weight . The people that are in the middle
50- 100 billion fat cells, ten to be over weight and have problem with weight. Well
and people with 200 billion fat cells always fail on weight loss diet. So for the
longest time it was thought that there is nothing you can do. You were born with
200 billion fat cells, and so you are stuck. And then came Gene Nightich?? Who
founded weight watcher. She used to be very overweight - morbidly obese. And
what she did was that she went on a diet in a bureau of nutrition in NYC ,which by
the way no longer exists . And she lost weight on this program . She then called it
weight watchers. So you could get it free at bureau of nutrition, or you can pay for
that. She lost weight and kept it off for a long time. She had eventually measured
her fat cells, and sure enough she had 200 billion fat cells. So then gee, she had all
those fat cells, and she still lost weight. Why is that? The reason is because of
developmental reasons in terms of fat cell. The fat cell theory says that we have 2
different types of fat cell growth. But be careful, this is not just in the fat cell
theory, this is the theory of any cell.
There are 2 types of growth in cell
a) hyperplasia
b) hypertrophic
All cells undergo this growth. The fat cell theory though says that hyperplasia -
increase in the number of cells, happens in certain stages in life. In other words, you
are born with certain number of cells-plateau. Hyperplasia can take place during the
-third trimester of pregnancy
- first year of life
-roughly between 9 and 13
- and also for women in postpartum.
So if a woman gains large amount of weight- woman is supposed to gain 24-26 or
not more than 30 lb during pregnancy. So we are talking about abnormal weight in
the third trimester, it will affect her’s and the baby’s fat cell number. If the woman
gains weight postpartum, it can increase her fat cell number as well. If the baby is
over fed during the first year of life, it can increase its fat cell number, and if the
child is overfed right before puberty between 9-13 that child can also increase its
fat cell number. So the fat cell theory says that there are certain critical periods of
life when you can increase your fat cell number.
Now Hypertrophic- increase in cell size is different . The size can get bigger
any time. So any time you eat more then you need, you will have increased cell size.
But you can have increased cell number only in those particular times. So they found that
you can be born with extra fat cells , or you can be born with normal amount of fat
cells. But overfeeding in those particular times, will cause you to have increase in
cell number, and any time you over eat, you can have increase in cell size!! But not
cell number.
When you go on kcal controlled diet or weight loss diet, you don’t loose fat cells,
you loose cell size. They will shrink in size. So how come they don’t stay that way? Why
is that 99% of those who go no wt loss diet. gain their wt back? There are some people in
whom leptin stops being produced when they loose certain amount of fat from their fat
cells, and then they will always feel hungry. The fat cell now will not make leptin
which functions as satiety trigger, and so you will newer feel full. This then is the
bodies way of saying I am starving.. So this theory focuses on fat cells, and it says
that once the fat cell become small enough, which may not even be at weight that
you want to be , leptin will stop being produced by the cell and you feel incredibly
hungry. If you have talked to somebody who was on weight reduction diet and lost
weight rapidly, they will tell you that they went on binge after that, and started
eating uncontrollably ” I couldn’t stop, I was always hungry” Some physicians are
now saying that there is physical reason for obesity , and it takes partly the stigma
from someone so that you don’t have those feelings where they just say you are just
out of control.
So when you look at people that lost weight , yes they lost weight,
but they still have those fat cells, and one of the things that you need to remember
about fat cell is that they, just like closets, want to be filled. As soon they start
losing fat, leptin will stop being produced in the body.
What happened next is that people said, lets see what happens with people who
gained weight over particular period of time. So lets say that somewhere in your mid
life, you had some kind of shocking event and you eat a lot. Since you you never had
a weight problem before , you would gain weight, but then you would loose it very rapidly
as supposed to someone who gained wt during pregnancy or immediately after
pregnancy. So again you can see how the number of fat cells made the big
difference. Then someone said that maybe we should stop looking at fat, and start
looking at something else. The something else was lean muscle . That’s how they
came up with the set point theory.
Set point theory
Set point theory goes along and was partly substantiated by the discovery of the OB
gene and leptin. What the set point theory says is that the body has a set wt . The wt
is made up of fat and lean muscle .We cant really look at water, because we are
always 65% water. If we are not 65% water we are in lots of trouble. So the body
has a set wt . It has a fair amount of lean muscle and set amount of fat. Through
homeostasis the body maintains that. Homeostasis is made up of all the different
things that we find in metabolism, all those chemical reaction. The body basically
likes to stay about 10% of the mid point of that set wt. So say as an adult you
arev150 lb. Your body will be ok at 135 and 165. But if you get less than 135
something happens. What generally happens is you get very hungry, and that’s
related to leptin . The other thing that happens is that BMR decreases. For people
that weigh more than 10% of their normal weight. For instance there is some kind
of trauma and you start eating more and you put on wt. It seem like that at 165 Lb
your BMR increases, and your weight starts creping back. Now again this si for
somebody that is at stable body wt. We are not looking at YO-YO dieter that is
going with his wt up and down. But even obese people are usually able to loose
about 10 or so % of their body weight without being too uncomfortable . But then
when they get below that, its harder to loose it , it takes longer to loose it, and they
are hungry all the time. That’s when people stop following their program, and go
back to unhealthy ways of eating . So that’s what the set point theory is talking
about. And agin this set point will be related to all the other chemical reaction in the
body. So the hypothalamus is the appetite control center of the body, and controls
the hunger. But it is actually related to the number of the fat cells, lean muscle
mass, whether we have the ob gene producing sufficient amount of leptin, whether
we have leptin receptor sites, and all these things. So in other words somebody is
not just obese because they have eaten too much and they cant control their
appetite. But that doesn’t mean that there aren’t people out there, that are over
weight because they eat too much and they don’t exercise. Those are however
whole different group of people than what we are talking about. Those are people
that have reactive obesity as suppose to developmental obesity .
Developmental obesity is hyperplasia, reactive obesity is hypertrophic. So lets say
you were normal wt and when you turn 25 you start gaining wt lets say 10 lb every decade.
Well one of the initial reasons you are gaining wt so steadily is that your basal
metabolic rate is decreasing. Some people says over the age of thirty or 25 . But
something else is happening to you. You are not a kid any more, and you have other
responsibilities. So you are not exercising any more. If you live somewhere else
then NYC you probably are in a school system that support athletic activities , you
are active . In NYC we don’t have that kind of luxury. But all of a sudden when
people are out of school, they don’t exercise as much, they stop. So not exercising
as much, they don’t burn Kcal. That is one thing . So that’s reactive. That has
really little to do with OB gene, leptin or anything like that. That is hypertrophic. So
these people can loose weight and keep it off as long as they take in not more then
what they need. The problem is though that our diet has changed and its not the %
of fat , CHO and protein , but we have increased the total number of Kcal that we
have been eating in the past decade. And we have fatter foods, or more kcal dense
food, and also the portion size is way larger. Now when we are talking about
portion size, I don’t mean portion size, that is on the food label. The portion size I
mean is the amount that’s now for somebody acceptable, or that they expect . If
they don’t get it, they feel that they have been gift. Fat free foods always have less
fat, but they have the same or no change in kcal. They replace the kcal from fat
with sugar. So that you eat the same amount, but because it was fat free, people
say I can eat the whole cake, rather then just one slice. And also because there was
no fat, you didn’t get filled up and you didn’t have the same satiety level .
Now there are all different ways to loose weight. There are many ways how to
loose weight rapidly, and then there are ways how to loose weight slowly. What the
problems are with rapid wt loss is the phenomena known as JO-JO dieting.. And this
is basically when you loose 10 lb and then you gain 15 lb back and again loose 10 lb
and again gain 15 lb.What you will see is that you are slowly gaining on weight. If
you talk to people who diet frequently, this is generally what they go though. And
this is simply because when they get below their set point, their BMR drops. This is
due to adaption, and it is because they are only dieting.
One of the things that happens when people only diet. and don’t exercise is that
about 50% of the wt loss is muscle. As we talked the other day, BMR is completely
dependent upon lean muscle mass .So when you are losing wt and it is muscle, your BMR
will drop. So what starts happening is that people will stop losing wt even on low Kcal
diets .If you get towards 1200 kcal, that’s not a lot of food, and you will feel hungry.
You can eat truck load of lettuce, and it will not make you feel full. Your body will go
into adaptive thermogenesis, its gona shut down its production of heat, and all the
kcal you take in will go to fat , because it wants to survive. That’s why it is
important for people not to diet alone , but to exercise in terms of losing wt.
Now there are all kinds of diets on the market, and the problem is that people
want to lose wt now, not later. And you can tell them that you can guarantee them
that they loose 30 lb in 60 days, but they will probably gain it back, or that they will
loose 30 lb over year and never gain it back. Just about all of them will apt for losing
it in 60 days. And the reason is because it is a human nature- “oh I will loose it and
keep it off” rather than “why do I have to wait a year”. Because of that human
nature, that wants things immediately, there are all kinds of diets on the market and
most are successful because they are low in Kcal. It doesn’t matter if its Atkins
diets or any other. So for the longest time low Carbohydrate and high protein diets
were always big sellers. People went on them and they lost weight very rapidly. The
reason for that is that we all need carbohydrates for our nervous system and red
blood cells. If you don’t get it from your diet, the body has to get it from somewhere
else. So one of the first places that you can get it from is glycogen. For every gram of
Glycogen there are 3 grams of water, so for every molecule of glycogen there are 3
molecules of water attached to it. So if you burn glycogen you have diuresis - you
get rid of water. So the very first thing that happens is that you loose water. The
second thing that happens is that once you go into dehydration and you loose about 2
% of your body wt in water, which is substantial , what happens is that the kidney
say something is wrong here, the body is dehydrated. One of the reasons it thinks the
body is dehydrated is - where is most of the water stored?-in the blood. So there is
less blood volume going through your kidney glomerulus. What’s gona happen is
that you your kidney will make less urine, and the kidney are going to start excreting
sodium into urine. When body will excrete Na, it will take some water with it as
well. So after a while you will keep on dehydrating your body. Also you need
glucose and where are you going to get it from if you are not getting it from food?
You will get it from protein . Then after a while you will get glucose from fat.
When you are on low CHO and high protein diet you will get eventually into
Ketosis. Ketosis indicate illness When people have ketones in their blood, urine and
breath they don’t think clearly and their personality changes- they become very
irritable. These diets make sure that you are in the ketosis They say that to stay in
the Zone you need to be in Ketosis. Why would you want to be in the zone of
illness? It is not healthy. These low CHO and high protein diets keep you in ketosis
which evens acidosis .When you are in acidosis one of the things that makes you
follow this diet is that you loose hunger, you loose your appetite. If you talk to
people that are in ketosis because they are protein malnourished, they have diabetes
or they have renal failure , they will tell you that it is hard to get them to eat. They
have no appetite.. You know that when your blood PH drops from normal PH 7.3 to
lets say 6.8, cells cannot exist in this acid environment and they die. Why would you
want to put your body to acidosis that is not good for your body??
If you look at Zone diet or any of the other diets you will find that those diets
are anywhere from 1200-1500kcla = low in kcal, that’s why you loose wt. Besides other
things, this diet causes large loses of calcium from the body and basically you loose 3x
the amount of calcium on 30% protein as is recommended in the Zone diet ,as you would
loose on the recommenced 8-12% protein in regular diet. You are in calcium balance if
your total kcal coming from protein are in the range of 8-12%. Once you go over this
range you get into negative calcium balance. If you look at these diets they will tell
you that you have to eliminate milk from your diet because it contain CHO.The
calcium content of these diets is then low.
Even though they initially loose wt, they will eventually gain it back. They gain
more, and they get depressed. So one of the thing we need to do is to get people to
visualize what wt really is. That by losing a lb or 2 or 3 it really does make a big
difference. That pound of fat is really big.
Try to get them to visualize what pound of chop meat looks like, and tell them to put
it somewhere on their body. Then try to get them visualize what it would look like to
loose that pound of chop meat. Its just something to get them something they have
seen. So you tell them that if they can loose this in a week , it will make a difference
for them .
It all comes down to behavioral change and the # 1 behavioral change that
you want them to do is exercise. But this is very hard to do. Excise meaning not just
aerobic exercise, but also weight training that builds muscle mass . It doesn’t burn
kcal, this is done through aerobic exercise. And the only way to lover the set point is
with exercise . There is no food that lowers set point. So exercised is one thing.
On the other hand people have to get used to what acceptable portion size is. A
pound of fat is 3500kcal . If you eat extra 500 kcal a day you will gain a pound of fat a
week .If you decrease 500kcal a day you will loose a pound a week. But that’s sometimes
difficult to do so. If you decrease 250 kcal through exercise, you will loose ½ a
pound a week , so to get people cut down a little bit on Kcal from food and then
exercise a little bit. As we said 250 kcal = about 2 miles walking. Very intensive
exercise burn CHO, low moderate exercise burn fat. So it is true the longer you
exercise, the more fat you will loose. But for many people it’s difficult to fit that into
schedule.
What you will see more is people that will drive 4 blocks to go and get
milk. Our society is very sedentary. In other places we could talk about suburban
obesity, because in those places people really need car to get to places, and so their
activity is not so great.
One little note before we finish today is that working with obese adults is really
next to impossible,while working with obese children is very rewarding.
For more information on obesity go to New York Times
Links to more information on Obesity
Physiology of obesity -GREAT ARTICLE ON OBESITY!!!
Dietfraud -web site about diets and scams
Weight Control and Obesity Topic Page (Food & Nutrition Information Center
Textbook on Obesity Obesity Education Initiative Electronic Textbook
WEIGHT LOSS METHODS - Weight loss tips
Popular diets on the market
Fad diet review
Understanding Adult Obesity
Mediterranean diet: Consider the benefits
ketogenic diet-its use for epilepsy in children frequently asked questiones
Journal of Obesity Research - Official Journal of NAASO
JOURNA-INTERNATIONAL JOURNAL OF OBESITY- register for free
Obesity Research journal full text