Obesity and Physical Activity. CHAPTER 22 Overview Obesity –Terminology –Prevalence –Control...

Obesity and Physical Activity

CHAPTER 22 CHAPTER 22 OverviewOverview

• Obesity– Terminology– Prevalence– Control of body weight– Etiology– Health problems– Treatment– Physical activity

Obesity:Obesity:Terminology and ClassificationTerminology and Classification

• Overweight– Body weight exceeds standard weight for given

height and frame size– Not precise terminology– Does not account for body composition

• Obesity– Excessive body fat (men >25%, women >35%)– Borderline obese: men 20 to 25%, women 30 to

35%

Obesity:Obesity:Terminology and ClassificationTerminology and Classification

• Body mass index (BMI)– Body weight in kilograms/(height in m)2

– Most widely used standard for obesity classification– Does not account for body composition– Overweight: 25.0 to 29.9 kg/m2

– Obese: 30.0+ kg/m2

• BMI classification cut points change for difference races and ethnicities

Table 22.2Table 22.2

Obesity:Obesity:Prevalence in the United StatesPrevalence in the United States

• Prevalence dramatically since ~1980– Prevalence of overweight has not changed much– Obesity continues to increase

• More prevalent in some races and ethnicities– Mexican-American men– Black women

• Increasing prevalence in children and teens

Figure 22.1Figure 22.1aa

Figure 22.1Figure 22.1bb

Figure 22.1Figure 22.1cc

Figure 22.2Figure 22.2


Obesity:Obesity:Prevalence in the United StatesPrevalence in the United States

• With age: fat mass , lean body mass – Over age 25, average person gains ~0.7 to 1 lb per

year– Up to 33 extra lb by age 55

• Will have significant effect on health care– Earlier onset of obesity– Increasing rates of obesity– Earlier onset of obesity-related diseases

Obesity: Obesity: Worldwide PrevalenceWorldwide Prevalence

• Increases in obesity not unique to United States– Canada, Australia, Europe have seen increases to a

lesser degree– Available data vary– Most recent studies show obesity spreading to all

regions of the world


Obesity:Obesity:Control of Body WeightControl of Body Weight

• Body usually carefully balances kilocalorie intake and expenditure– Gain of 1 lb/year represents imbalance of 3,111 kcal

per year– Body can balance to within 9 kcal per day

• Body may regulate around set point using– Resting metabolic rate (RMR)– Thermal effect of meals (TEM)– Thermal effect of activity (TEA)


• RMR– Body’s metabolic rate in the early morning– 60 to 75% of total energy expenditure

• TEM– Energy expended to digest, store nutrients, etc.– 10% of total energy expenditure– May be defective in obese individuals


• TEA– Energy expended to accomplish activities– 15 to 30% of total energy expenditure

• Balance of RMR, TEM, TEA– Helps body adapt to or kilocalorie intake– Controlled by sympathetic nervous system– Key for maintaining weight around set point



• Set point regulation versus weight gain– Diet composition alters set point– Physical activity alters set point– High-fat diets usually overfeeding

• Other factors– Larger portions/restaurant supersizing– Higher fat consumption– More eating away from home

Obesity:Obesity:EtiologyEtiology

• Physiological factors– Heredity/genetics– Hormonal imbalances– Altered basic homeostatic mechanisms

• Lifestyle factors– Cultural habits– Inadequate physical activity– Improper diets


Obesity:Obesity:Health ProblemsHealth Problems

• Morbidity: presence or rate of disease

• Mortality: death from disease

• Obesity and overweight mortality

• Major increased risk: BMI >35



• Obesity and overweight associated with– Cardiovascular disease– Type 2 diabetes– Cancer (endometrial, breast, colon)– Liver, gallbladder disease– Osteoarthritis– Sleep apnea

• Metabolic syndrome rate parallels obesity

Obesity:Obesity: Genetic Versus Lifestyle Effects Genetic Versus Lifestyle Effects

• Pima Indians: study in genetics versus lifestyle

• Native lifestyle lean and healthy• Western diet/lifestyle high rates of obesity

– Men: 64%– Women: 75%

• Obesity often accompanied by diabetes– Men: 34% – Women: 41%

Obesity: Obesity: Genetic Versus Lifestyle EffectsGenetic Versus Lifestyle Effects


• Changes in normal body function– Vary with individual– Vary with degree of obesity

• Lethargy

• Polycythemia

• Low blood O2/high blood CO2

• Clotting, heart failure


• Body fat distribution: disease risk factor– Upper-body (android) obesity (men)– Lower-body (gynoid) obesity (women)

• Waist:hip girth ratio and visceral fat index identify fat distribution

• Android obesity higher risk for– Cardiovascular disease– Elevated blood lipids– Diabetes


Figure 22.8Figure 22.8aa

Figure 22.8Figure 22.8b-cb-c


• Exacerbates existing diseases

• Weight loss reduces severity of– Angina pectoris– Hypertension– Congestive heart disease– Heart attack recurrence– Varicose veins– Diabetes– Orthopedic problems


• Emotional and psychological factors– Can help cause obesity– Can be exacerbated by obesity

• Obesity = social stigma– Media glamorize thin people– But norms may shift as obesity becomes more

common

Obesity:Obesity:General TreatmentGeneral Treatment

• Weight loss = kilocalorie intake < kilocalorie expenditure– Oversimplification– Weight loss treatment multifactorial

• Loss not to exceed 1 to 2 lb per week– Weight loss a long-term project– Maintain balanced diet with caloric deficit– Reduce intake of fat and simple sugars


• Hormone treatments– Decrease appetite– Increase RMR– Serious side effects, life threatening

• Surgical treatments– Intestinal bypass– Gastric banding or bypass– Reserved for most extreme, serious cases


• Behavior modification: change in eating patterns or habits. Examples:– Can only eat in one location– No snacking– No second helpings

• Appealing, simple weight loss approach

Obesity: Role of Physical Activity Obesity: Role of Physical Activity in Weight Controlin Weight Control

• Overeating and inactivity: major causes of obesity

• Kilocalorie restriction and exercise best treatments

• Exercise alters body composition– Significant long-term kilocalorie deficit– Significant long-term fat loss

• EPOC postexercise metabolism


• Body mass and composition changes with exercise– Total weight

– Fat mass, percent body fat– Maintained or FFM

• Changes long term (6-12 months)


• Both aerobic and resistance training weight loss– Exercise important aspect of weight loss– Must combine exercise + kilocalorie restriction– Decrease rate of visceral fat accumulation

• Energy balance equation– Kilocalorie intake – kilocalories excreted = (RMR +

TEM + TEA)– Helps clarify weight loss mechanisms


• Exercise effects on appetite– Leads to appetite suppression in male animals– Leads to no change or intake in female animals– Less activity ≠ less food intake

• Causes for appetite suppression– Higher circulating catecholamines– Higher body temperature


• Exercise effects on RMR– May increase with training– Resistance training of interest (RMR related to FFM)

• Exercise effects on TEM– Pre- and postmeal exercise TEM– Chronic exercise training inconclusive

• Exercise effects on fat mobilization– During exercise, FFA mobilization – Possible causes: hGH, sympathetic stimulation,

catecholamines


• Spot reduction a myth– Local exercise ≠ local fat loss– Exercise draws on all fat stores– Local exercise local muscle development

• Spot reduction studies– Tennis: dominant versus nondominant arms– Intense sit-up training program


• Low-intensity aerobics and weight loss– High intensity percent energy from CHO

oxidation– Low intensity percent energy from fat oxidation– Low intensity no change in total fat kilocalories

expended– Low intensity in total kilocalories expended

• Fatmax zone– Zone where fat oxidation rates near peak

– 55 to 72% VO2max




• Exercise gimmicks ineffective. Examples:– Mark II Bust Developer– Astro-Trimmer Exercise Belt– Slim-Skins Vacuum Pants

• Reality: exercise and weight loss require work

Obesity: Physical Activity Obesity: Physical Activity and Health Risk Reductionand Health Risk Reduction

• Exercise risk of disease mortality– Irrespective of weight loss– Good news for those who struggle with weight loss

• Active lifestyle and fitness more important

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Obesity and Physical Activity. CHAPTER 22 Overview Obesity –Terminology –Prevalence –Control...

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