Transcript Chapter 4

Judith E. Brown
www.cengage.com/nutrition/brown
Obesity to Underweight:
The Highs and Lows of Weight Status
Unit 9
Prof. Albia Dugger • Miami-Dade College
Variations in Body Weight
• Body processes that favor food intake and
body-fat storage developed when “feast and
famine” cycles were common
• In the US, the proportion of overweight and
obese people is increasing, and underweight
people decreasing
Weight Status
• Science defines
standards for body
weight based on the
risk of death
• Risk increases for the
overweight and
underweight
Body Mass Index
Know This:
• Body mass index
(BMI)
• An indicator of body
weight status based on a
person’s height
• Calculated as kilograms
per meter squared
• Estimate of body fat
content
BMI Chart
Most US Adults Weigh Too Much
• 66% of US adults are overweight or obese
• 1 in 6 children are overweight
• Overweight
• High weight for height
• Obese
• Condition characterized by excess body fat
Overweight and Obesity Increasing
Obesity Rates Vary by State
Obesity Increasing Worldwide
• Overweight and obesity
is becoming a major
health problem in the
US and around the
world
Obesity and Health
• Obesity increases risk
of many diseases by
altering metabolism
Key Terms
• Metabolism
• Chemical changes that take place in the body
• Example:
• Conversion of glucose to energy or to body fat
Metabolic Abnormalities
• 70% of obese people have metabolic
abnormalities that increase disease risk
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Hypertension
Elevated triglycerides, glucose, or insulin
Low HDL-cholesterol (“good cholesterol”)
High C-reactive protein (inflammation marker)
• 10-15% weight loss decreases risks
Key Terms
• C-reactive protein (CRP)
• Key inflammatory factor produced in the liver in
response to infection or inflammation
• Elevated concentrations are associated with heart
disease, obesity, diabetes, inactivity, infection,
smoking, inadequate antioxidant intake
Obesity and Psychological Well-Being
• Prejudice against children
• Unfair treatment from teachers
• Isolation, rejection, feelings of inferiority
• Prejudice against adults
• Discrimination in hiring and promotion
• Considered lazy or lacking self-control
Body Fat and Health
• Health problems associated with obesity are
related to where excess fat is stored
Know This:
• Subcutaneous fat
• Fat under the skin
• Visceral fat
• Fat under the skin and muscle of the abdomen
Subcutaneous and Visceral Fat
Body Shapes
• “Pear shape”
• Fat primarily in hips, upper arms and thighs
• Less visceral fat, lower risk
• “Apple shape”
• Fat primarily in abdomen
• More visceral fat, higher risk
Pear and Apple Shapes
Risks From Visceral Fat
• Visceral fat is metabolically active and
strongly related to many diseases
• Causes chronic inflammation, insulin resistance,
metabolic syndrome, elevated blood glucose and
triglycerides, high blood pressure and hardening
of arteries
• Leads to heart disease, some cancers, type 2
diabetes, hypertension, fatty liver disease
Key Terms
• Chronic inflammation
• Long-lasting, low-grade inflammation
• Inflammation
• First response of the immune system to infection
or irritation
• Triggers release of biologically active substances
that promote oxidation and other harmful
reactions in the body
Key Terms
• Metabolic syndrome
Know This:
• A group of metabolic abnormalities characterized
by insulin resistance, abdominal obesity, high
blood pressure and triglycerides, low HDL
cholesterol, impaired glucose tolerance
• Predisposes people to type 2 diabetes, heart
disease, hypertension, and other disorders
• Common in the US (1 in 5 adults)
Key Terms
• Insulin resistance
• Condition in which cells “resist” the action of
insulin in transporting glucose into cells
• Fatty liver disease
• Fatty infiltration of the liver (≥10% of weight)
• Associated with obesity, diabetes, alcoholism
• Steatohepatitis (fatty liver with inflammation)
Visceral Fat and Waist Circumference
Know This:
• Waist measurements of excess visceral fat:
• Men: > 40 inches (102 cm)
• Women: > 35 inches (88 cm)
• May not accurately measure visceral fat in
large, muscular individuals
Determining Waist Circumference
Determining Waist Circumference
• Japan requires adults
age 50-74 to have
yearly waist
measurements
Assessment of Body Fat Content
• Measures of body fat content are better
estimates of health status than BMI
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Skinfold thickness measures
Bioelectrical impedance analysis (BIA)
Underwater weighing
Magnetic resonance imaging (MRI)
Computerized axial tomography (CT scan)
Dual-energy X-ray absorptiometry (DEXA)
Whole body air displacement (BOD POD)
Assessment of Body Fat Content
Assessment of Body Fat Content
Assessment of Body Fat Content
Assessment of Body Fat Content
Assessment of Body Fat Content
Assessment of Body Fat Content
Everybody Needs Some Body Fat
• Body fat has essential
functions
• Hormone manufacture
• Cell structures
• Cushions organs
Know This:
What Causes Obesity?
• Factors that contribute to excess body fat:
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Diet
Physical activity
Environmental exposures
Genetic background
Some medications
Born to Be Obese?
• Genetic traits influence a person’s
susceptibility to becoming obese
• Inborn errors in metabolism (rare)
• Predisposing traits with environmental triggers
• Environmental trigger
• Environmental factor such as inactivity, high-fat
diet, or high-sodium intake that causes a genetic
tendency to be expressed
Do Obese Children
Become Obese Adults?
• 8% of obese 1-2 year olds who do not have
obese parents become obese adults
• 80% of obese 10-14 year olds who have at
least 1 obese parent become obese adults
Diet and Obesity
• Weight gain results when more energy is
consumed than expended
• Americans’ calorie intake has risen
• Inexpensive, energy-dense foods
• Fast-food restaurants, all-you-can-eat buffets
• Large portions of food
Inactivity and Obesity
• Low levels of physical activity contribute to the
high and increasing incidence of obesity
• Few voluntary activities
• Driving instead of walking or biking
• TV watching related to childhood obesity
Preventing Obesity in Children
• Lifestyle changes for the whole family
develop healthy eating and activity habits
• Nutritious food selections
• Fun physical activities
• Avoid negative focus on weight
Preventing Obesity in Adults
• Weight gains likely between ages 25-34
• Slow weight gain (about 1 pound/year)
• Some gain large amounts over short periods
• Actions need to be taken
• Regular vigorous exercise
• Reduce portion sizes
• Get 8 hours of sleep
Changing the Environment
• Environmental changes can be made
• Limiting access to “junk food” in schools
• Requiring calorie labels in fast-food and chain
restaurants
• Development of urban community gardens
• More sidewalks, bicycle and walking paths
• Smaller portions and more nutrient-dense foods in
restaurants
Some People Are Underweight
• Causes of underweight in developed nations
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Illnesses (HIV/AIDS, pneumonia, cancer)
Eating disorders (anorexia nervosa)
Voluntary food restriction
Poverty
• Unhealthy underweight causes fatigue,
illness, bone fractures, poor concentration
Defining Underweight
• Underweight Know This:
• Low weight-for-height
• BMI <18.5
• May represent a deficit of body fat
• Men <5%
• Women <12%
Underweight and Healthy
Know This:
• About 2% of people
with low BMIs are
genetically thin and
healthy, with normal
body composition
Underweight and Longevity
• A nutritious, calorierestricted diet extends
life in mice and
monkeys
• People who voluntarily
calorie restrict appear
thin but healthy
Realistic View of Body Weight
• People come in many sizes and shapes
Size Acceptance
• Natural weights and shapes can’t be modified
very much
• US obsession with weight and shape
promotes eating disorders, social problems
• Society can help by accepting people of
different weight and sizes
The Health at Every Size Program
• Health at Every Size Program
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Reduces health problems associated with obesity
Reduces blood pressure and LDL-cholesterol
Increases HDL-cholesterol
Improves self esteem and body image
Decreases disordered eating behaviors