ChapterChapter 8 8Energy Balance and Body CompositionEnergy Balance and Body Composition

BombCalorimeter

How Do We Know How Much Energy Comes From A Food?

Calorimetric Values

versus

Physiological Fuel Values

Physiological Influences - empty stomach & gastric contractions - absent of nutrients & GI hormones - endorphins (brain’s pleasure compounds)

Cognition Influences - presence of others (social occasions) - perception of hunger or time of day - abundance of food or free food

Hunger

Satiation

Seek Food

ContinueMeal

MealEnds

Postingestive Influences - presence of food triggers stretch receptors - nutrient in intestine elicit hormones such as CCK

Postabsorptive Influences - nutrients in blood signal brain - as nutrients diminish, satiety diminishes and hunger developsSatiety

Message Central

Hypothalamus - involved in controlling water

balance, regulation of body temperature and appetite control

e.g. Leptin - protein hormone produced by adipose cells - acts on the hypothalamus - promotes negative energy balance by suppressing appetite & increasing energy metabolism

So we know where Energy Imput comes from but….. Where Does the Energy Go?

Basal Metabolism: - energy to run activities such as:-- maintaining body temperature-- keeping autonomic systems (lungs, heart, kidneys, blood cells production, etc)

Factors That Affect BMR

- Height - Age and Body Composition - Growth Rates - Fever - Stresses - Environmental temperature - Fasting / Starvation - Malnutrition - Nicotine and Caffeine - Sleep

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BMR(Basal Metabolic Rate)

BMR varies with body size and shape due to surface area

Factors That Affect BMR

- Height - Age and Body Composition - Growth Rates - Fever - Stresses - Environmental temperature - Fasting / Starvation - Malnutrition - Nicotine and Caffeine - Sleep

So we know where Energy Imput comes from but….. Where Does the Energy Go?

Physical Activity

Thermic Effect of Food

BMI (The Body Mass Index)

BMI values

18.5 25 30

ObeseOverweightHealthy

Underweight

Pounds (without clothes)

Hei

gh

t (w

ith

ou

t sh

oes

)

Body Compositions Compared

Fat Muscle Bone Organs

% B

od

y M

ass

Healthy and Obese Body Compositions Compared

% B

od

y M

ass

Fat Muscle Bone Organs

% B

od

y M

ass

Fat Muscle Bone Organs

Women Men

HealthyObese

HealthyObese

% Body Mass

Mo

rtal

ity

Body Mass Index versus Mortality

Health Risks Associated with Body Weight and Body Fat

Underweight

- depends on the reason why an individual is underweight

- individuals can be underweight and healthy

- however, often underweight is due to malnutrition, smoking habits, or illness.

Health Risks Associated with Body Weight and Body Fat

Overweight

- diabetes, hypertension, cardiovascular disease and stroke, apnea, osteoarthritis, cancer, and complications during surgery or pregnancy.