HSC 215: Exam 3
Section 1: Weight Management
General Obesity and Weight
Determined by BMI and waist circumference
Obesity may affect everyone (children included)
Being found at a younger age
Causes are multifactorial
Linked to psychological and physiological conditions
People gain weight as they age, then lose it as older adults
Obesity in Youth
Obesity affects everyone, including children
Obesity and chronic diseases/conditions are being found in younger individuals
Hypertension and Type 2 diabetes are more common in young adults now
Older adults may outnumber younger adults in coming decades
Environment
We live in an obesogenic environment
Our obesogenic environment enables…
the overeating of high calorie, tasty foods
avoiding physical activity
sitting too much
We used to be physically active, hunting and evading predators
Genetics
BMI heritability: 40-70 percent
Around half your weight status and body composition comes from your genes
Genetic links to obesity:
Body size
Body fat storage depot
Resting metabolic rate
Difficulty gaining/losing weight
Energy
Diets in high fiber and protein have a lower glycemic index,
Linked to satiety (helps align your energy intake with energy expenditure)
Energy expenditure components:
Resting metabolic rate
Thermic effect of activity
Food processing costs
Energy density is determined by the number of calories per gram of food.
Foods with low calories (e.g high water content) mean you can have larger portions
RMR
The most energy is expended through Resting Metabolic Rate (RMR)
RMR = 60-70% of daily energy expended
Higher RMR = Higher energy body uses at rest
Lots of energy needed to maintain vital functions when at rest
RMR is influenced by…
Hormones: Thyroid and sex hormones
Age: Decreases with age
Environment: Very hot or cold environments
Exercise & Physical activity: RMR elevated for hours by intense exercise, consistently elevated in highly active people due to increased lean body mass
Weight Change: Decreases with weight loss
Thermic Effect
Thermic Effect of Activity (TEA): All muscle contractions that use energy above RMR (e.g., sitting, typing, walking, exercising).
The most adjustable factor in energy expenditure on daily basis
Energy expenditure: Depends on mode, intensity, and body size
Ex. A large person with more lean mass spends more energy for a given weight-bearing activity than a small person does.
Thermic Effect of a Meal: The small energy cost of food processing includes
Chewing
Digesting
Transporting
Metabolizing
Storing ingested calories
It takes more energy to process protein than other kinds of food.
The total energy used is minimal—only 10 percent of energy intake.
Healthy Energy Balance
Don't lose more than 1--2 lbs a week
Rapid weight loss hard to maintain, disrupts RMR, loss of muscle and bone mass
Reduce energy intake and increase energy expenditure. (Burn more than you take in)
Small reductions in weight (3 to 5 percent of body weight) reduce risk for several chronic diseases if done by improving diet and moving regularly
Calorie intake depends on:
body size, activity level, age, and other factors.
No less than 800 daily calories
Very-low-calorie diets are unsustainable; they set you up for failure.
Expending Energy
Aerobic Endurance Activities: Improve cardiorespiratory health + use a lot of energy
Higher intensity + longer duration = more energy spent + increase influence on RMR
Resistance training = maintaining muscle mass metabolic activity
Prescription Drugs & Surgery
Prescription drugs may influence energy consumption, energy expenditure, and interfere with energy absorption.
Bariatric surgery = last resort for morbidly obese people
Reduces stomach size to reduce food intake
Drugs + Surgery combined with behavior modification for long term management
Stress, Sleep, Alcohol
All carry important implications for weight management
Influence energy in and out
Stress:
Increases choosing to eat starchy, sweet food (junk food)
Being stressed for time may cause you to chose processed/fast food
High stress leads to fatigue which reduces motivation to move and leads to more sitting
Fatigue:
Reduces motivation to stick with healthy food choices
Increases intake of caffeine which increases energy intake if consumed in sweet drinks (e.g., soda, sweetened coffee).
Alcohol:
Too much alcohol = fatigue, reduces interest in exercise, causes dehydration
Preventing Weight Gain
Energy expenditure in preventing weight gain is not well established because of challenges with study designs.
High levels of activity reduce declining RMR after middle age by maintaining muscle mass and keeping muscle mass metabolically active.
Cardiorespiratory and resistance training helps protect against reductions in RMR that occur with weight loss.
Moderate- to vigorous-intensity aerobic activities for 30 to 60 minutes per day on at least five days per week
Activity allows you to eat more (i.e., restrict energy intake less).
Promotes the healthiest body-composition change (preserving muscle mass and reducing bone loss).
Exercise and physical activity are even more important for weight-loss maintenance.
Increased cardiorespiratory activity is needed for weight-loss maintenance (60 minutes per day).
Perform moderate- to vigorous-intensity activities on at least five (and closer to seven) days per week and progress to 250 minutes per week.
Body Image & Eating Disorders
Includes perceptions, images, evaluations, and feelings about our appearance (entire body or certain part).
Positive body image is essential to psychosocial well-being and successful weight management.
Negative body image can cause mental anguish, damage self-esteem, interfere with healthy relationships and social activities, and lead to depression.
Negative body image and unhappiness with weight status = eating disorders and other unhealthy weight-management behaviors.
Eating disorders are increasingly common among men and women of all ages.
The most common disorders related to negative body image are anorexia, bulimia nervosa, binge-eating disorder, and exercise addiction.
Professional Help
Psychologist or therapist: Helps address eating disorders and misuse of food or activity to manage stress or emotions.
Registered dietitian nutritionist (RDN): Helps with personal dietary plans.
Certified fitness trainer: Helps set up a program or improve your adherence.
Medical evaluation: Helps if your weight changes for no apparent reason or does not change in response to intentional manipulation of energy intake or expenditure.
Summary
Weight management is hard in our obesogenic society with easy access to food and little need to use energy to survive.
To manage weight, we must attend constantly to the energy balance equation, especially energy intake and energy expenditure through physical activity and exercise.
Movement, especially cardiorespiratory and resistance training, can enhance your weight-management success.
Knowing when to seek professional assistance may be a key part of your weight-management program.
Section 2: Body Composition
Body Composition General
Body comp includes: Fat, muscle, and bone mass
Relate to primary diseases of obesity, sarcopenia, and osteoporosis.
Models include:
Most Common: the two-component model, which divides the body into fat and fat-free components
Gold standard: four-component model that divides the body into water, protein, fat, and bone mass.
Three-component model: divides the body into fat mass, lean soft tissue (including muscle), and bone mass—relates to health, especially for young adults.
Fat
Fat stores energy, cushions organs, and helps regulate body temperature.
Contained in all cell membranes
Essential fat = fat needed for healthy body function
Men: 3-5%
Women: 8-12%
Most fat available (stored energy) located in adipocytes
Most fat storage located right under the skin (subcutaneous fat) or deep in the abdomen (visceral fat)
May be located in liver, around heart, near bundles of muscle fibers (ectopic fat)
Influenced by genetics
Women vary in fat patterns, genetically inclined to a specific fat pattern
Android/Apple (male) fat pattern: Extra weight in midsection
Gynoid/Pear (Female) fat pattern: Extra weight in hips and thighs
Fat depots carry varying risks for health
Body Types
Most have a blend of two body types
Some do not match a particular type
Endomorph: Roundest, wide shoulders and hips,
(re)Gain weight easily
Excel in strength activities (ex. lifting)
Challenged by weight bearing exercise (ex. distance running)
Mesomorph: Muscle, broad shoulders, lean, muscular
Respond readily to exercise training
Excel at exercise and sports
Manage body composition easily
Ectomorph: Thin, linear, narrow shoulders and hips
Little fat or muscle
Excel at weight bearing exercises
Body Composition Methods
Measured in many ways
Most commonly facilities use two and three component models
Measure whole body or regions of body
All have some degree of error
More expensive equipment and sophisticated expertise provide more accurate estimates.
DEXA estimates have an error margin of only 1 to 2 percent.
Many BIA instruments have an error rate of 4 to 5 percent.
Water Submersion
Hydrodensitometry: Two component model - Fat and fat free
Body density = degree of body fatness
Body density ranges from .9 gm/dL (purely body fat) 1.1 gm/dL (purely fat free)
Underwater weighing requires complete submersion in tank of water while weight is obtained on a scale
Density = Mass / Volume
Density calculated by the difference between weight on land and weight underwater.
Once body density is determined a prediction equation can be used to estimate relative adiposity, or percent body fat (%Fat).
Air Displacement
Air displacement plethysmography similar to underwater weighing
Replaces water with air to determine body density
Uses a closed chamber called a BOD POD to acquire body density.
The person being measured wears minimal clothing, removes air from the hair by wearing a swim cap, and sits very still.
BOD POD chamber uses computerized sensors to measure changes in air volume
Value of body density is entered into an equation to estimate %Fat.
Approach is safer and more comfortable than underwater weighing, especially for children, older adults, people with movement disabilities, and those afraid of water.
Dual-Energy X-Ray Absorptiometry (DEXA)
Exposes the body to low- and high-energy X-rays.
Provides both whole-body and regional (arm and leg) estimates of body composition.
Valid and reliable method for estimating body composition.
Easy to perform ( requires lying still on a scanning table for a few minutes).
Downsides include high cost, necessity of expertise, and radiation exposure (a small amount).
One of the best technological advances for estimating body composition
Three-component model, measures fat mass, lean soft tissue (muscle), and bone mass.
Available in nearly all hospitals and in many university departments of exercise science and nutrition.
Magnetic Resonance Imaging (MRI)
Shows ectopic adipose depots (where only small amounts of fat should be stored), including visceral fat (deep in the abdomen)—a major health risk.
Can be used to assess fat infiltration into muscles (intermuscular adipose tissue) which has been linked to higher risk for metabolic diseases and poor muscle quality.
Available in most hospitals and many research centers.
Bioelectrical Impedance Analysis (BIA)
Suitable for laboratory, field, and personal use
Based on the fact that nearly all body water is contained in fat-free mass; thus measuring body water enables us to estimate fat-free mass.
Bioelectrical instrument sends a small electrical current through the body and measures the resistance to the current.
Resistance to current is determined by the balance between water (a great conductor) and fat (a good insulator).
Measures water so the person being tested must be properly hydrated; being dehydrated or overhydrated can greatly affect accuracy.
Lower-cost BIA instruments offer a less accurate measure of total body water and %Fat.
Skin Fold
Used to assess body composition as stored fat is located just beneath the skin.
Skinfold thicknesses obtained from several sites and summed; the total reflects overall skinfold thickness, which represents % Fat.
Standardized measures can be taken on the legs, arms, back, and abdomen.
Skinfolds should be measured by high-quality calipers.
Obtaining valid and reliable measurements requires much practice on various body types.
Skinfold assessment requires the measurer to touch the person being measured on multiple parts of the body, which some may find uncomfortable.
Research-grade calipers can cost several hundred dollars; well-calibrated spring-loaded ones are also expensive.
When converting a skinfold sum into a %Fat estimate, the tester must choose from numerous prediction equations, which can influence accuracy.
Cannot measure visceral adipose tissue, which is located beneath the muscle wall of the abdomen.
Weight Status
Method will depend on…
your purpose
the availability of equipment
testing expertise
amount of money you can or want to spend.
At a minimum, you should monitor your weight and waistline.
Weight status is evaluated primarily based on BMI which hinges on the ratio of weight to height.
Waist circumference is highly related to visceral fat. Weight status is influenced by diet (especially salty and starchy foods), weather, stress, and hormonal changes.
4 S’s of Weight Status
Same time of day
Same day each week
Same clothing (or none!)
Same scale
BMI
Based on the ratio of weight to height (weight in kilograms divided by the square of height in meters).
Classifications: underweight, normal weight, overweight, and obese
Due to the link between waist size and visceral fat and the related risk for metabolic diseases, risk is estimated based on BMI and waist circumference.
A person with normal BMI can be at an increased risk for disease due to an elevated waist size.
BMI is related strongly to % Fat across all age groups, doctors use it to assess health status.
BMI levels in the overweight and obese categories are linked to increased risk of chronic disease and death in most adults
Risk is also influenced by many other factors:
physical activity and exercise
diet quality
Smoking
alcohol and drug habits
stress.
Heavily muscled athletes: Increased muscle mass increases weight, thereby increasing BMI as well.
Altered height: We lose several inches as we age; therefore, if our weight is stable, our BMI increases.
Reduced physical activity: The relationship between BMI and %Fat can be altered by reduced muscle mass in individuals who are bedridden or unable to walk due to illness, spinal cord injury, or other challenges.
Chronic Illness
Body composition is linked directly to primary diseases.
Too much fat mass (high %Fat) is defined as overweight or obesity.
Overweight is linked to many chronic diseases and conditions that occur in middle age and beyond.
Having too little muscle mass and low bone mass can cause serious conditions and diseases that often arrive later in life.
%Fat
% Fat has no universally accepted norms.
10-22 % Fat for men
20-32 % Fat for women is optimal
A slight increase (of 3 to 5 %Fat) is a normal part of the aging process.
A % Fat level below 3 - 5 for young men or 8 - 12 for young women can be harmful to health.
Fat Deposits
Location of fat storage influences a person’s risk for many chronic conditions and diseases.
Where fat is stored (as an adolescent) is dependent on
genetics and sex hormones
level of physical activity, diet quality, and stress hormones. (Lesser extent)
Changes in whole-body composition during the aging process shift the preferred fat storage depot more centrally and less in the lower body
Sarcopenia
Age-related loss of muscle mass and strength.
Risk increases with age (45-65)
Major cause of functional decline and loss of independence in older adults.
Muscles retain ability to get stronger well into our 90s
Osteoporosis
Screening occurs based on age and health history.
The DEXA instrument measures bone mass and bone density.
Bone density T-score value is primary tool for diagnosing osteoporosis.
T-score of −2.5 or below indicates being 2.5 standard deviations below the peak bone density of a young healthy person of the same sex.
Risk factors:
Age: (Primary risk factor as bone loss naturally occurs as we age)
Sex: Women have a greater risk due to bone size and differing sex hormone profiles
Race or ethnic group: White and Asian people have greater risk of osteoporosis than do African-American people.
Diseases, conditions, and medical procedures: Increased risk with cancer, endocrine or hormonal disorders, autoimmune disorders, and digestive disorders
Medications: Bones can be compromised by many medications (e.g., steroids)
Nutrition: Bone health is directly affected by poor intake of calcium and vitamin D
Physical activity and exercise: Bone health is greatly affected by being sedentary (especially if bedridden)
Benefits of Healthy Body Composition
Energetic physical function
Enhanced work, recreation, or sport performance
Healthier self-esteem and self-image
Prevention of the big metabolic three and physical-function diseases and conditions
3 Legged Stool
Body comp management 3 Legged Stool:
Exercise and physical activity
Adequate nutrition
Appropriate hormones
Physical activity and exercise:
Fat mass: Choose high-energy activities. Endurance activities expend many calories, and energy balance is crucial for maintaining a healthy level of fat mass.
Lean soft tissue (mainly muscle). Relatively high-intensity strength training is the most effective mode for gaining and keeping muscle mass.
Bone mass and density. Bones must be loaded in order to adapt
Nutrition
Adequate protein intake is important for muscle maintenance and bone health
Calcium and vitamin D are critical for bone health.
Poor dietary habits (along with physical inactivity) are major reasons for rising rates of obesity, sarcopenia, and osteoporosis.
Hormones
Differences in fat, muscle, and bone mass seen in men and women during and after puberty are greatly affected by sex hormones, testosterone and estrogen, and other growth hormones.
Age-related declines in these hormones constitute a key reason for changes in body composition (increase in fat mass and decreases in muscle and bone mass).
Female Athlete Triad
Disordered eating (with a range of poor nutritional behaviors)
Amenorrhea (irregular or absent menstrual cycle)
Osteoporosis (low bone mass and poor bone quality, thus leading to weak bones and risk of fracture) Though most common in women, it also occurs in men who aim to compete in weight-class sports.
Summary
Body composition is the fifth and final component of health-related physical fitness.
Primary components are body fat, muscle mass, and bone mass.
Body composition can be measured in the research lab or the privacy of your home.
Optimal nutrition and regular physical activity and resistance training can go a long way toward successful management of body composition.