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Chapter 10

Lecture Slides

Weight Control

• Weight control for health

– Mental health • Body image

• Fattism

– Physical health • Obesity

• Anorexia

• Weight control for performance

– Weight-control sports • Running

– Muscle-mass sports • American football

Body Weight and Body Image

• Dissatisfied with current body weight

– 40% of American men

– 55% of American women

– Many high school and elementary school students

• Desire to change current body weight

– 85% of first-year male and female college students

• Females: Leanness

• Males: Muscularity

Obesity

• World Health Organization

– 1 billion people overweight

– 300 million are obese

Obesity • United States

– Rate of obesity increasing over past 30 years

– 2 out of 3 adults are overweight or obese

– Extreme obesity increasing at alarming rates • 1 in 200 in 1986

• 1 in 50 today

– Overweight and obesity increasing rapidly in children • About 25% will be overweight or

obese by 2015

Body Weight and Composition What is the ideal body weight?

• Ideal for what?

– Health

– Appearance

– Sport performance

• Concept of Healthy Body Weight

– The Body Mass Index (BMI)

• Also known as Quetelet’s Index

Body Mass Index

• A height to weight ratio

– Body weight in KG ÷ (Height in meters)²

– Body weight in lbs x 705 ÷ (Height in inches)²

• Normal BMI = 18.5 – 25.0

What are the values and limitations of the BMI?

• Value

– A screening device for both underweight and obesity, both of which may be related to health problems

– May be a useful guide to body weight for the average individual

• Limitations

– Does not evaluate body composition

• Some classified as overweight may have low body fat

• Some classified as normal weight may have excess fat

What is the composition of the body?

• The human body is composed of earth’s elements

– Carbon, hydrogen, oxygen, nitrogen

– Calcium, phosphorus, iron, magnesium, and others

• Elements in combination

– Carbohydrate

– Fat

– Protein

– Water

– Minerals

Body composition components

• Four major body components and their densities

– Density = mass ÷ volume [g/ml or g/cc)

• Body water (Density = 1.0)

• Total body fat (Density = 0.9)

• Fat free mass (Density = 1.1)

• Bone mineral (Density = 1.3 – 1.4)

• Determination of body composition is usually done by calculating total body density

Body composition

• Total body fat

– Essential fat

• Males (3%)

• Females (12-15%)

– Storage fat

• Subcutaneous fat – Cellulite

• Visceral fat

Body composition

• Fat-free mass

–Protein and water

– Lean body mass

• Includes essential fat

Body composition

• Bone mineral

– 50% water

– 50% protein and minerals

– Total bone weight, including protein and water, may constitute 12-15% of body weight

Body water

• Body water compartments

– Intracellular

– Intercellular

– Extracellular

• Normal water levels

– 60% of body weight in average-weight male

– 50% of body weight in average-weight female

• Fat-free mass and body fat

– Muscle is about 70% water

– Fat is about 10% water

What techniques are available to measure body composition and how accurate are they?

• Direct analysis of body fat

– Chemical extraction

• Indirect analysis of body fat

– All techniques currently used with living humans are indirect

– All techniques are subject to measurement error

– Two-component models have highest error

– Three- and four-component models help reduce error

Body composition • Measurement error

– Standard error of measurement (SEM)

– May vary with body fat measurement techniques

• Normal curve – 70% of population within ± 1

SEM

– 95% of population within ± 2 SEM

• Assume skinfold technique predicts 17% body fat and SEM is 3% – 70% chance body fat is between

14-20%

Underwater weighing

• Hydrodensitometry

• Based on Archimedes’ principle

– Buoyancy of water displacement

• Previously was the gold standard

• SEM is about 2.0 - 2.5%

Air Displacement Plethysmography (APD)

• Based on air displacement

• Advantages over underwater weighing

• Reliable method in testing same subject over time

Skinfolds technique

• Measure of subcutaneous fat

– Skinfold calipers

– Ultrasound

• SEM about 3-4%

• Use population-specific formulae

• Good practical method

• Used by NCAA for wrestlers

Dual Energy X-ray Absorptiometry (DXA;DEXA)

• Computerized X-ray

• Concurrent measures

– Bone mineral

– Body mat

– Fat-free mass

• Some contend it is the criterion method

• Others

– Computed tomography

– Magnetic resonance imaging

Body composition

• Other methods

– Bioelectrical impedance analysis

– Infrared interactance

– Anthropometry

• Regional fat distribution

• Waist circumference

– Multicomponent models

• Use combination of methods

• Some consider it the new gold standard

What problems may be associated with rigid adherence to body fat percentages in sport?

• The SEM for the measurement technique may be high

• Example of potential problem

– Skinfold technique predicts body fat as 8% in young athlete

– Coach wants athlete to reduce to 5%

– If SEM is 3%, the athlete may already be at 5%

– Losing excess weight in such an athlete may come at the expense of losing muscle tissue

How much should I weigh or how much body fat should I have?

• A complex question

• Physical appearance

– Individual’s perception

– May lead to health problems

• Sport performance

– May be benefits of weight

loss or weight gain

• Health

– Some guidelines for health

improvement

Body mass index

• Screening for health

• Some classify a BMI of 35 or 40 as morbid obesity

BMI Health Risks

< 18.5 May signal malnutrition or serious disease

18.5-24.9 Healthy weight range that carries little health risk

25-25.9 Overweight; at increased risk for health problems, especially if you have one or two weight-related medical conditions

Above 30 Obesity, more than 20 percent over healthy body weight; poses high risk to your health

Body fat percentage

• Recommendations for health /performance vary

Waist circumference

• Measure of regional fat distribution

Regulation of Body Weight and Composition

How does the human body normally control its own weight?

• Male college student

• Consume about 1 million Calories a year

– 2,700 Calories daily

• Not gain one pound

• Set-point theory

– Energy intake balanced with energy expenditure

– Role of the hypothalamus

The set-point theory of weight control

Comparable to the set-point for temperature control.

Instead of a set point for body temperature, there is a

set point for body weight

The set-point theory: Energy intake

• Appestat

– Hunger center

– Satiety center

• Afferent stimuli

– Senses

– Stomach fullness

– Blood nutrient levels • Glucostat; lipostat; aminostat

– Body temperature

– Hormones and neuropeptides (neurotransmitters)

The set-point theory: Energy expenditure

• Basal energy expenditure (BEE)

– Brown fat

• Uncoupling proteins (UCP)

• Uncouple oxidation from ATP formation

– White fat tissue and muscle tissue

• UCPs

– Hormones

• Thyroid hormones; epinephrine

The set-point theory: Energy expenditure

• Nonexercise activity thermogenesis (NEAT)

– All activity except sleeping, eating, and sports-like exercise

The set-point theory: Feedback control of energy intake & expenditure

• Short-term mechanisms – May ↑ or ↓ food intake

– Expansion or contraction of stomach

– Peptides

• Cholecystokinen, obestatin terminate meal

• Ghrelin stimulates the appetite

– Changes in blood glucose or amino acids • May regulate carbohydrate and

protein intake

The set-point theory: Feedback control of energy intake & expenditure

• Long-term mechanisms

• Role of leptin

– Hypothalamus neurons make neuropeptide Y (NPY)

– NPY secretion stimulates appetite

– Leptin is released from adipose cells

– Leptin inhibits NPY secretion

The set-point theory: Feedback control of energy intake & expenditure

• Long-term mechanisms

• Role of leptin

– Increases in body fat will increase leptin release, decreasing the appetite

– Decreases in body fat will decrease leptin release, increasing the appetite

• The development of leptin resistance is thought to be a cause of obesity

The set-point theory: Feedback control of energy intake & expenditure

• Long-term mechanisms

– An activity-stat has been proposed

– May involve secretion of dopamine in the brain

– Decreased energy expenditure will stimulate physical activity

– Increased energy expenditure will induce physical inactivity

How is fat deposited in the body?

• Hyperplasia of adipose cells

– Increase in number of adipose (fat) cells

– May be important in childhood obesity

– Appears to occur throughout life

• Hypertrophy of adipose cells

– Increase in amount of fat per adipose cell

– Maximal amount appears to be 1 mcg of fat per adipocyte

• May be a genetic predisposition to more adipose cells

What is the cause of obesity?

• The simple answer

– Energy intake exceeds energy expenditure

• The difficult answer

– Involves a complex interplay of both genetic and environmental factors

Genetic factors

• Heredity is an important factor in etiology of obesity

– Studies with identical and fraternal twins

– Body composition of children related more to biological parents as compared to adoptive parents

Genetic factors

• Obesity genes have been identified; over 340 in the Human Obesity Gene Map

– Abnormalities in neural function leading to increase energy intake; neural tracts that are difficult to change

– Decrease protein receptors for leptin; leptin resistance may develop, thus NPY continues to stimulate the appetite

Genetic factors in weight gain

• Human Obesity Gene Map

– A predisposition to sweet, high-fat foods

– Impaired function of hormones such as insulin

– Decreased levels of human growth hormone

– Low plasma leptin concentrations

– Greater number of fat cells

– An enhanced metabolic efficiency in storing fat

– A lower resting energy expenditure (REE)

– Lower levels of spontaneous physical activity, or NEAT, during the day

– Lower levels of energy expenditure during light exercise

Environmental factors

• Environmental factors also highly involved in the development of obesity

• “The marked increase in obesity worldwide appears to be attributable to a modern society that explicitly encourages the consumption of supersized portions of high-fat, high-sugar foods while implicitly discouraging physical activity.

Thomas Wadden

University of Pennsylvania

Environmental factors in weight gain

• High-fat, high-Calorie foods

– High-fat foods

• Fat is palatable

• More Calories per gram

• May encourage overconsumption; less suppression of appetite

• Dietary fat may be stored more efficiently than carbohydrate or protein

Environmental factors in weight gain

• Fast foods

– High palatability

– High-fat content

– High-sugar content

– High energy density

Environmental factors in weight gain

• Low-fat, large-portion size, high-Calorie foods

– Liquid Calories

– 12-ounce bottle of sugar-sweetened soda

• 10 teaspoons of sugar; 150 Calories

• 20-ounce bottle; 250 Calories

– Sodas and other sugar flavored drinks thought to underlie increase rate of obesity in children

– Average American consumes 300 more Calories today than 15 years ago, mainly from carbohydrates

Environmental factors in weight gain

• Physical inactivity and NEAT

– Technological advances may decrease activities of daily living

– Decreasing levels of physical activity can contribute to weight gain

– One study with NEAT found that mildly overweight individuals stayed seated about 2.5 hours longer per day than lean individuals • Calculated this could lead to 350 fewer Calories expended per day

– Levine notes that NEAT may vary as much as 2,000 Calories per day among different individuals

Environmental factors in weight gain Other factors

• Sleep

– Reduced amount of sleep has been associated with overweight and obesity

– More tired and less likely to exercise

– More chances to eat

– Being overweight may cause sleep apnea

• Emotional stress

– Perceived as an emergency; body eats more and stores fat

– Cortisol may stimulate caloric intake and deposit fat in intra-abdominal fat depots

Environmental factors in weight gain Other factors

• Personal relationships

– Research suggests social and family relationships may contribute to weight gain

• Study of 12,000 subjects over 32 years

– Person’s chances of becoming obese increased by 57% if a close friend became obese in a given time frame

– Similar findings with siblings and spouses

Environmental factors in weight gain Other factors

• Drugs

– Alcohol

• Rich in Calories (7 per gram)

• Excess is stored as fat

• Alcohol intake does not suppress appetite or fat intake

– Nicotine

• May inhibit the appetite and increase REE

• Cessation of smoking may lead to weight gain

• Gain 11-13 pounds in 2 years

Interaction of Genetics and Environment

• Genes may be an important determinant of weight gain, but do not explain the rapid increase in obesity over the course of the past 20 years

• Environmental factors are more important, such as changes in lifestyle

– The “Freshman Fifteen” not quite that high, but more likely the “Freshman Five”

• Creeping obesity

– 100 Calories extra per day = 10 extra pounds per year

– 200 Calories extra per day = 20 extra pounds per year

Figure 10.7

Can the set point change?

• The settling-point theory

– Weight gain

• Genes may increase leptin resistance

• Body weight increases to new level

– Weight loss

• Resting metabolism may return to normal after initial decrease

– Prevention may be the key to weight gain and obesity

Why is prevention of childhood obesity so important?

• Current 16 % of overweight children will ↑ to 24% by 2015

• Neural circuits predisposing to obesity developed while young are not easily abolished – Obesity persists from preschool through elementary school and into

young adolescence

• Diet is a key factor in childhood obesity – Sugar-sweetened beverages

• Physical inactivity – Television viewing and similar sedentary behaviors

• Physical inactivity and diet – Children consume more Calories when watching TV

Weight Gain, Obesity, and Health

• Obesity may impair health in several ways

1. Increased mass of adipose tissue places strain on body tissues, such as the heart and joints

2. Increased number of adipose cells may secrete more adipokines, which may induce pathogenic processes such as inflammation

3. Adipose cells may convert androgen hormones to estrogen hormones, which may affect cellular processes

What health problems are associated with overweight an obesity?

• Health costs of obesity may parallel those associated with cigarette smoking

• $100 billion is estimated health costs of obesity-related health problems

– 5-10 % of annual health care costs

Possible health problems associated with overweight an obesity

• Asthma

• Cancer

• Cardiovascular disease

• Diabetes (type 2)

• Dyslipidaemia

• Gallstones

• Gastrointestinal reflux

• Gout

• Hypertension

• Insulin resistance

• Low self-image and

self-esteem

• Osteoarthritis

• Respiratory dysfunction

• Sleep apnea

• Social disabilities

• Stroke

• Vertebral disk herniation

Obesity and cardiovascular disease

• American Heart Association

– Obesity is a major risk factor

– 1% ↑ in BM! ↑ CHD risk by 5% - 7%

• Role of adipokines for CHD

– Harmful adipokines may be ↑ in the obese

– Promote inflammation and clotting

• Excess body fat also promotes risk factors for CHD

– High blood pressure

– Hypercholesterolemia

– Type 2 diabetes

• Diabesity

Obesity and cancer

• Obesity is a risk factor for certain cancers

• May account for 14% of cases in men; 20% in women

• Those with highest BMI (≥ 40) at greatest risk

• Recent American Institute of Cancer Research worldwide report found convincing evidence of a link between increased body fatness and several cancers – Breast

– Colorectum

– Pancreas

– Esophagus

– Kidney

Obesity and maternal health

• Overweight and obesity are associated with increased risk of stillbirth

– Recent meta-analysis of 9 studies

• OR of 1.47 in women who were overweight

• OR of 2.07 in women who were obese

Obesity: Mortality, morbidity, and quality of life

• Overweight may increase risk of premature mortality, but not as great as obesity

• Obesity may contribute to 300,000 deaths annually in the United States

– BMI of 30-35 is high risk of death

– BMI > 35 accounts for largest majority of deaths

• Projected years of life lost with severe obesity at ages 20-30

– White men: 13 years White women: 8 years

– Black men: 20 years Black women: 5 years

How does location of body fat affect health?

• Regional fat distribution

– Android-type obesity

• Abdominal region

• Visceral fat

– Gynoid-type obesity

• Gluteal-femoral region

• Hips, buttocks, thighs

Android-type obesity

• Android-type fat cells (deep visceral fat cells)

– Release adipokines harmful to health

• Trigger inflammation and coagulation

• Induce insulin resistance (resistin)

– Decrease release of adiponectin, a protective adipokine

• May lead to the metabolic syndrome

The Metabolic Syndrome

• Metabolic syndrome

– Cardiometabolic syndrome

– Syndrome X

• Cluster of symptoms

– Hyperinsulinemia

– Insulin resistance

– Impaired glucose tolerance

– Increased small, dense LDL-cholesterol

– Decreased HDL-cholesterol

– Hypertension

– Increased plasma fibrinogen and clotting

The Metabolic Syndrome

• Increased risk of CHD and type 2 diabetes

• 25% of American adults have 3 or more components of the metabolic syndrome

– Individuals with a normal (18.5-24.9) or overweight (25.0-29.9) BMI with high waist circumference may have several of the components of the metabolic syndrome

The Metabolic Syndrome

• New classification system

• Waist circumference and two of four components

Men Women

Waist circumference (inches) 37 31.5

Elevated serum triglycerides (mg/dL) 150 150

Subnormal HDL-cholesterol (mg/dL) < 40 < 50

Elevated blood pressure (mmHg) 130/85 130/85

Elevated fasting blood sugar (mg/dL) 100 100

The Metabolic Syndrome

• Android-type obesity is a major risk factor for mortality in both men and women

– Increased risk of CHD and cancer

– Even among normal-weight women

• However, weight loss via dieting and exercise appears to preferentially decrease abdominal fat

– Small weight losses can reduce several of the risk factors in the metabolic syndrome

Does being obese increase health risks in youth?

• Psychological problems

– May impair self-image and self-esteem

– May avoid physical activities and miss the socializing aspects of play

• Physical health problems

– High blood pressure

– Type 2 diabetes

– May lead to health problems

in early adulthood

Does losing excess body fat reduce health risks and improve health status?

• Weight loss is one of the major recommendations of health professionals as a means to enhance health

– American Heart Association

– American Institute of Cancer Research

– American Diabetes Association

• Diet plans

– The DASH diet

– The OmniHeart diet

Does being physically fit negate the adverse health effects associated with being overweight?

• Some scientists contend that being overweight does not increase risk of mortality if various risk factors, such as blood pressure and serum lipids, are normal

• Increased physical activity may reduce various risk factors even though weight is not lost

– Increase insulin sensitivity

– Decrease blood pressure

– Increase self-esteem

• However, benefits of exercise work best when excess body fat is lost

Fitness and Fatness

Unfit and Fat

•Highest mortality rate

Unfit and Not fat

•Lower mortality rate

Fit and Fat

•Lower mortality rate

Fit and Not Fat

•Lowest mortality rate

Active at Any Size

Weight Control Information Network

www.win.niddk.nih.gov

• Click on “Publications for the Public” to access Active at any Size, a program to help encourage and help overweight individuals plan an exercise program.

Excessive Weight Loss and Health What health problems are associated with

improper weight-loss programs and practices?

• Weight loss: Health; Appearance; Sport performance

• Improper weight-control programs

– Dehydration

– Weight-loss dietary supplements

– Weight-loss drugs

– Very-low-Calorie diets

– Weight cycling

– Young athletes

Dehydration

• Excessive dehydration

– Exercise

– Sauna

– Diuretics and laxatives

– Possible heat illnesses

• Case study with bodybuilders

– Diuretics and potassium supplements

– Hyperkalemia maybe fatal

Weight-loss Dietary Supplements

• Numerous over-the-counter (OTC) products

– Lose 30 Pounds in 30 Days

• Most OTC weight-loss supplements do not appear to be effective

• More research needed with some

– Pyruvate and CLA

• Some herbals may be dangerous

– Ephedra

– Others associated with liver damage

Weight-loss Drugs

• Available for use in the United States – Sibutramine (Meridia)

• Inhibits uptake of neurotransmitters; suppresses appetite

• Stimulate thermogenesis

– Orlistat (Xenical)

• Block gastric lipases; inhibit fat absorption

• alli (OTC version)

• Europe – Rimonabant (Acomplia)

• Suppresses the appetite

• Nicotine patches may help prevent weight gain with smoking cessation

• Drug use optimal when used with lifestyle changes

Very-Low-Calorie Diets (VLCDs)

• Modified fasts

– < 800 Calories per day

– May be successful under medical supervision

– Used as a first step in weight-loss programs

• Possible problems

– Weakness Constipation

– Loss of libido Decreased HDL

– Decreased blood volume Cardiac arrhythmias

• Best when coupled with lifestyle changes

Weight cycling

• The Yo-Yo syndrome

– VLCD followed by high-Calorie diet

– Cycles of weight loss followed by weight gain

• Previous research suggested

– May lead to decrease in REE

– Weight gain may contain more fat, less muscle

• Current research reveals

– No adverse effects of weight cycling • Weight gain does not exceed weight loss

• More research needed to explore health effects

Young athletes

• Making weight for sports

– Possible inadequate intake • Protein

• Iron, calcium, zinc

– Possible effects of a combination of intense training and insufficient energy intake • Inhibition of hypothalamus and pituitary gland

• Suppressed sexual development

• Restricted growth

– ACSM: Does not appear to affect growth in wrestlers

– May pose a problem in young female gymnasts

What are the major eating disorders?

• Disordered eating

– Less severe than full fledged Eating Disorders

– American Psychiatric Association (APA)

• Eating Disorders Not Otherwise Specified (EDNOS)

– Purging disorders

• Eating disorders (APA)

– Anorexia nervosa (AN)

– Bulimia nervosa (BN)

– Binge eating disorder (BED)

Anorexia nervosa (AN)

• Compulsive personality disorder

– Not completely understood

• Strong genetic predisposition

– Identical and fraternal twin studies

– Genes may be linked to appetite control

APA Criteria for Anorexia nervosa

• Refusal to maintain body weight over a minimal normal weight for age and height

• An intense fear of gaining weight or becoming fat, even though underweight

• A disturbance in the way one’s body weight or shape is perceived

• Amenorrhea, or the absence of at least three consecutive menstrual cycles in normally menstruating females.

Anorexia nervosa

• Prevalence is relatively low

– Primarily females under the age of 25

– 1% or less of the general population

– As high as 2% in college students

• Strong genetic predisposition

– Identical and fraternal twin studies

• Chronic low self-esteem

• Serious medical consequences

– Anemia

– Decreased heart mass

– High risk for suicide

Anorexia nervosa

• Therapy for AN may require hospitalization and intensive psychiatric treatment for both the patient and family

• The outcome for females with AN has changed little over the past 50 years

• Mortality is high

– AN with lowest body weight at highest risk

APA Criteria for Bulimia nervosa (BN)

• Recurrent episodes of binge eating, at least two per week for 3 months.

• Lack of control over eating during the binge.

• Regular use of self-induced vomiting, laxatives, diuretics, fasting, or excessive exercise to control body weight.

• Persistent concern with body weight and body shape.

Diagnostic and statistical manual of mental disorders (Fourth edition)

Bulimia nervosa

• Bulimia nervosa means morbid hunger

– Loss of control over the impulse to binge

– Binge-purge syndrome

• BN is more common than AN

– 2-3% of the general population

– One estimate suggests up to 10% of college students

• Medical consequences of vomiting and laxatives

– Erosion of tooth enamel

– Tears in esophagus

– Electrolyte imbalances

• Psychological counseling may help; Prozac use has been approved

APA Criteria for Binge Eating Disorder (BED)

• Eat more quickly than usual during binge episodes

• Eat until they are uncomfortably full

• Eat when they are not hungry

• Eat alone because of embarrassment

• Feel disgusted, depressed, or guilty after eating

Binge Eating Disorder (BED)

• Individuals with BED have behaviors common to BN, but do not purge

• Health consequences include

– Weight gain and obesity

– Increased risk of CHD and cancer

• Treatment is similar to BN

What eating problems are associated with sports?

• Eating Disorders Not Otherwise Specified

• Anorexia Athletica

• Weight loss as an ergogenic aid

– Wrestling

– Gymnastics

– Cheerleading

– Bodybuilding

– Lightweight football and rowing

– Distance running

Anorexia Athletica

Five set criteria

• Excessive fear of becoming obese

• Restriction of caloric intake

• Weight loss

• No medical disorder to explain leanness

• Gastrointestinal complaints

Additional criteria (1 or more)

• Disturbance in body image

• Compulsive exercising

• Binge eating

• Use of purging methods

• Delayed puberty

• Menstrual dysfunction

Eating disorders in sports

• Estimates of prevalence vary

– NCAA study

• 20-40 % of female college athletes may exhibit criteria of eating disorders

• 50-70 % in certain sports, such as gymnastics

– One study of NCAA Division I athletes

• 10% with symptoms of bulimia nervosa

• 3% with symptoms of anorexia nervosa

• Symptoms of eating disorders may abate at the end of the competitive season

The Female Athlete Triad

The Female Athlete Triad

• Disordered eating

– Low energy availability

• Amenorrhea

– Disturbance of hypothalamus-pituitary-ovary axis

– Primary or secondary • 3-6 months or more between periods

• Osteoporosis

– Decreased estrogen from the ovaries

– Low body fat so less conversion of androgens to estrogen

– Estrogen is involved in bone metabolism

The Female Athlete Triad

• Prevention involves education of those involved sports

– Coaches, athletic trainers, administrator, parents

• What to look for

– Unexplained weight losses

– Frequent weight fluctuations

– Sudden increases in training volume

– Excessive concern with body weight

– Appearance, and evidence of bizarre eating practices

The Female Athlete Triad

• Treatment

– Counsel with the athlete

– Increase dietary energy intake

– Decrease exercise-associated energy expenditure

• Mental health practitioners may be needed for athletes with eating disorders

Body Composition and Physical Performance

Weight control as an ergogenic aid

What effect does excess body weight have on physical performance?

• Excess body weight as fat or muscle

– Disadvantages

– Advantages

• Lose fat weight

– Enhance energy efficiency

– Improve appearance

• Gain muscle weight

– Increase power

– Increase stability

– Improve appearance

Excess body weight & physical performance

• Adverse effects of excess body fat or muscle mass

– May impair energy efficiency

– May detract from aesthetic appearance

Excess body weight & physical performance

• Beneficial effects of excess body fat or muscle mass

– May increase strength and power

– May increase stability

– May enhance aesthetic appearance

Weight Control for Performance

• Loss of excess body fat – In general, a 1% loss of excess body fat will increase

running speed by 1% (Craig Dean, Running Times) – Example:

• Current 10K race pace is 8:00/mile, or 49:36 • Lose 5% of excess body fat • Increase 10K race pace speed to 7:36/mile

– 8:00 (480 sec) x .05 = 24 sec; 8:00 – 0:24 = 7:36 – New 10K time is about 47:12

• Comparable improvements in the marathon (3:29:36 improves to 3:19:08) or 10 minutes faster

Body weight loss and physical performance

• Weight loss should be fat, not muscle involved in energy production

• Recall the limitations of body fat measurements as a means to predict body fat levels for sports performance

– May lead to excess weight loss and impaired performance

• Keep in mind that body composition is only one factor impacting sport performance

Does excessive weight loss impair physical performance?

• Improper weight-loss programs may impair performance

– Excessive dehydration

– Diuretics and laxatives

– Starvation-type diets

• Proper weight-loss programs

– Lose weight, mainly fat, gradually

– Prevent hypoglycemia

– Prevent dehydration

– Maintain lean body mass, or muscle