Transcript Chap9

Understanding Nutrition
Chapter 9
Weight Control:
Overweight and Underweight
By
A. Fellah, Ph.D.
A Fat Cell
Excess energy is stored in the fat cells of adipose tissue. The
amount of fat reflects both the number and the size of fat cells
An Adipose
Cell
An adipose, or
fat, cell seems
to expand
almost
indefinitely. The
more fat it
stores, the
larger it grows.
accommodate its swollen contents.
Fat Cell Metabolism
 Lipoprotein lipase (LPL) promotes fat storage in both adipose
and muscle cells.
 LPL is mounted on fat cell membranes.
 Obese people have many fat cells, they have more LPL
activities in their fat cells than lean people do.
 LPL activities is partially regulated by gender-specific
hormones-estrogen and testosterone.
 Lower body is less active than the upper body in releasing fat.
 Easily regain lost weight: LPL activity increases after weight
lose (the fatter the fastest).
Fat Cell Development
Fat cells are capable of increasing their size by 20-fold and their
number by several thousandfold.
Causes of Obesity
 Set Point: The point at which controls are set. The set-point theory that
relates to body weight proposes that the body tends to maintain a certain
weight by means of its own internal controls.
1. Genetics:
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Identical twins are 2x as likely to weigh the same as fraternal twins.
Genes may not cause obesity, but genetic factors may influence the food
intake and activity patterns and the metabolic pathways.
Liptin: a protein produced by fat cells under direction of the ob gene that
decreases appetite and increases energy expenditure.
• ob is the obesity gene that expressed in the fat cells which codes for
liptin.
• It acts as a hormone, in the hypothalamus.
• Mice with a defective ob gene don’t produce leptin and can weigh up
to 3x as normal mice and have 5x as much body fat.
A Model
of Leptin’s
effects on
Energy
Balance
and Body
Fatness
Leptin’s Action in the Body
Leptin maintains energy
homeostasis.
When the body gains fat,
the increase in leptin
shifts energy balance
toward the negative: eat
less and spend more
energy.
Such a scenario would
ensure that all fat gains
were followed by losses,
but this is not the case in
reality, of course.
When leptin levels are high, the hypothalamus
produces melanocortins, dampen appetite
Leptin’s Action in the Body
When the body loses
fat, the decrease in
leptin shifts energy
balance toward the
positive: eat more and
spend less energy.
• Most obese people have high levels of leptin, but their
energy balance does not automatically shift to the
negative, suggesting a resistance to leptin’s action in
obesity.
• When leptin is low, hypothalamus produces
neuropeptide Y, which stimulates appetite and slows
energy expenditure (Leptin inhibits neuropeptide Y
production)
 When leptin level is high, the hypothalamus produces
melanocortins, which dampen appetite and increases
energy expenditure.
Both mice are genetically Obese, they
lack the gene for Leptin
Receives Leptin
No Leptin
Mice with and Without Leptin Compared
Both of these mice have a
defective ob gene.
Consequently, they do not
produce leptin. They both
became obese, but the
one on the right received
daily injections of leptin,
which suppressed food
intake and increased
energy expenditure,
resulting in weight loss.
Causes of Obesity, cont.
2. Environment:
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Overeating:
• Overweight people overeat, whether this is true has
been difficult to determine.
•
Genetically obese rats eat much more than their
nonobese littermate at early age.
•
Overeating contributes to obesity, but does not fully
explain it.
•
Toxic food environment: a term coined to refer to
the easy access to and overabundance of high-fat,
high kcalories food in our society.
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Physical Inactivity:
• Modern technology has replaced physical activity at
home and at work.
• Remote control, escalators, automobiles, buttons, ……..
• Inactivity contributes to weight gain and poor health.
• Watching TV may contribute most to physical inactivity.
• People may be obese, not because they eat too much,
but because they move too little.
Pear Shaped Body
Basic body shapes. The
pear normally has
narrow shoulders, a
small chest, and an
average-size waist.
Fat is concentrated in
the hips and thighs.
Weight loss in these
areas is usually
difficult.
Pear Shaped Body
The apple looks round in
the middle.
Fat is concentrated in the
waist and can be lost
with diet and exercise.
Apple-shaped people are
at increased risk for
diabetes, hypertension,
high blood cholesterol,
and heart disease.
Waist to hip ratio
Body Fat Location Is Important to Health: Apple
The man on the left is 6 feet tall and weighs 240 pounds; the man on the right is
6 feet 1 inch tall and weighs 230 pounds. Although similar in weight and height,
the man on the left is at higher risk for diabetes, hypertension, and heart
disease due to his “apple” shape and body fat content.
Controversies in Obesity Treatment
 Elusive Goals:
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Every overweight person can achieve
slenderness and should pursue it.
Only 5% of all people who successfully lose
weight maintain their losses for at least a
year.
 Dangers of Weight Loss:
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Fad Diets: often sound good, but fall short to delivering on
their promises.
• Adverse reactions from headache to death.
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Weight Cycling: repeated cycles of weight loss and gain,
yo-yo effect.
• Increase the risks of chronic disease and premature death.
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Psychological Problems:
• Most weight-loss programs assume that the problem can be
solved simply by applying willpower and hard work.
• Ineffective treatment and its associated sense of failure add to a
person’s psychological burden.
The Weight Cycling Effect of Repeated Dieting
Each round of
dieting is followed
by a rebound of
weight to a higher
level than before.
Obesity in Adults
Prevalence of overweight among adults in the United States
Gradual Weight Loss Increases Success
People who lose weight gradually are more likely to keep it off than those who
lose weight rapidly. The weight loss graphed here averages a quarter pound
per week.
The Psychology of Weight Cycling
Shows how the devastating psychological effects of obesity and
dieting perpetuate themselves.
Aggressive Treatments of Obesity
1. Drugs:
 An effective drug that can used over time without adverse
side effects currently doesn’t exists.

Sibutramine: suppresses appetite by inhibiting the uptake of
serotonin in the brain, suppressing appetite.
• Effective when used with a reduced-kcalorie diet and physical activity.
• Dry mouth, headache, constipation, insomnia, and high blood
pressure.

Orlistat: Inhibits pancreatic lipase activity, thus block fat
digestion and absorption by 30%.
• Effective with a reduced-kcalorie diet, low fat diet.
• Gas, frequent bowel movement and reduced absorption of fat soluble
vitamins.
Diet Aids
• Herbal Products:
St. John’s wort: contains substance that enhance
serotonin which suppress appetite.
Weight Loss Drugs
There is no lack of weight-loss books and products. There is a
lack of approaches that help people keep weight off.
Weight-Loss Products
A few examples of
bogus weight-loss
products that were
removed from the
market.
Weight-Loss Products: Herbal
A few examples of
bogus weight-loss
products that were
removed from the
market.
2. Surgical Procedures Used in Treatment of Obesity
The dark pink areas
highlight the flow of
food through the GI
tract. Notice that the
procedure maintains a
relatively normal flow.
The pale pink areas
indicate the sections
that have been
bypassed.
Surgical Procedures Used in Treatment of Obesity
The dark pink areas
highlight the flow of
food through the GI
tract. Notice that the
flow bypasses most of
the stomach, all of the
duodenum, and some
of the jejunum.
The pale pink areas
indicate the sections
that have been
bypassed.
Gastric Bypass Surgery
Weight Goals and Expectations Compared
Reasonable weight goals and expectations compared.
Reasonable Treatments of Obesity
 Eating Plans:
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Be involved in planning.
“Energy out” should exceed “energy in” by about 500 kcal/day.
Make nutritional adequacy a high priority.
Emphasize nutrient-dense foods.
Eat small portions. Share a restaurant meal with a friend or take home
half for lunch tomorrow.
Limit low-fat treats to the serving size on the label.
Make legumes, whole grains, vegetables, and fruits central to your diet
plan.
Eat slowly.
Limit high-fat foods.
Limit concentrated sweets and alcoholic beverages.
Drink a glass of water before you begin to eat and another while you
eat. Drink plenty of water throughout the day (8 glasses or more a day).
Reasonable Treatments of Obesity, cont.
 Physical Activity:
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Activity and Energy Expenditure.
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Activity and Basal Metabolism.
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Activity and Appetite Control.
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Activity and Psychological Benefits.
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Choosing Activities.
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Spot Reducing.
Physical Activity Guidelines
People’s bodies are
shaped by the
activities they
perform.
Reasonable Treatments of Obesity, cont.
 Behavior and Attitude:
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Behavior modification: the changing of behavior by the manipulation of
antecedents (cues or environmental factors that trigger behavior), the
behavior itself, and consequences (the penalties or rewards attached to
behavior).
Behaviors change tip:
• Keep a record of diet and exercise habits; it reveals problem areas.
• Strategies:
Don’t grocery shop when hungry.
Eat slowly.
Exercise when watching TV.
• Learn alternative way to deal with emotions and stress.
• Attend support groups regularly or develop supportive relationships
with others.
• Adopt permanent lifestyle changes to achieve and maintain a health
weight.
Reasonable Treatments of Obesity, cont.
 To prevent excessive weight gain:
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Eat regular meal and limit snacking.
Drink water instead of high-kcalorie beverages.
Select low-fat foods regularly and limit dietary fat to 30% of daily kcalorie
intake.
Become physically active and limit TV viewing time.
 Underweight:
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It is a body weight so low as to have adverse health effects; it is
generally defined as BMI <18.5.
It is a far less prevalent problem than overweight, affecting ~ 5% of US
adults.
Thin people may find gaining wt difficult.
In wt gain or wt loss, physical activity and energy intake are essential
components to a sound plan.
Maintainers Versus Weight Regainers
Maintainers Versus Weight Regainers
Weight-Gain Strategies
 Eat energy-Dense Foods.
 Eat at least 3 meals a day.
 Eat large potions of food and expect to feel full.
 Eat snacks between meals.
 Drink plenty of juice and milk.
 Exercise and eat to build muscles.
The Female Athlete Triad
Eating Disorder Terms
•Anorexia Nervosa
•Binge-eating disorder
•Bulimia Nervosa
•Cathartic
•Cognitive therapy
•Eating disorder
•Emetic
•Female athlete triad
Eating Disorders in
Women
Eating disorders
occur in males as
well as females,
but females make
up approximately
95% of all cases.
Anorexia Nervosa
A day’s diet? For a person with anorexia nervosa, it was.
The foods shown provide approximately 562 calories.
Essential Features Helping to Diagnose
Criteria used for the diagnosis of anorexia nervosa.
Women with
anorexia nervosa
see themselves
as fat even when
they are
dangerously thin.
Essential Features Helping to Diagnose, con.
Diagnosis Bulimia Nervosa
Eating Disorders
The vicious cycle of restrictive dieting and binge eating.
Binge Eating Disorder
Binge Eating
Binge - Purge Disorder
The Clash Between Culture and Biology
The trend toward size acceptance. Acceptance of a realistic standard of body
weight and shape—one that corresponds to health and physical fitness—and
respect for people of all body sizes may be the most effective measures that
can be taken to prevent anorexia nervosa and bulimia nervosa.
Summary
 Various theories are used to explain obesity.
 Fat cell development, fat cell metabolism, and set-point theory
are theoretical explanations.
 Genetics and environmental factors have been proposed as
causes of obesity.
 Differences of opinion lead to controversies in weight loss
treatment.
 Choices for treatment of obesity are many.
 Aggressive treatments include drugs and surgery.
Summary
 Weight regains are common.
 Reasonable treatments for obesity involve planning
well-balanced eating plans with physical activity.
 Behavior and attitude are important aspects.
 Weight maintenance programs are valuable after
weight goals are met.
 Underweight conditioned pose health problems also.
 Strategies for weight gain include intake of energydense foods, regular meals, large portions, extra
snacks and exercise to build muscles.
Summary
 Anorexia nervosa, bulimia nervosa and binge
eating are eating disorders characterized by
sociological, neurochemical and
psychological problems.
 The nutritional component of treatment
involves dietary intervention and education.