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.