Judith E. Brown

Prof. Albia Dugger • Miami-Dade College

www.cengage.com/nutrition/brown

Obesity to Underweight:The Highs and Lows of Weight Status

Unit 9

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

• 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

Know This:

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•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

• Subcutaneous fat • Fat under the skin

• Visceral fat • Fat under the skin and muscle of the abdomen

Know This:

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 • 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)

Know This:

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

• 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

Know This:

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• 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:•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• 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• Low weight-for-height• BMI <18.5

• May represent a deficit of body fat•Men <5%•Women <12%

Know This:

Underweight and Healthy

• About 2% of people with low BMIs are genetically thin and healthy, with normal body composition

Know This:

Underweight and Longevity

• A nutritious, calorie-restricted 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•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