chapter 10 - energy balance & body composition Flashcards
energy balance
intake matches expenditure
positive energy balance
intake exceeds expenditure
negative energy balance
intake is less than expenditure
energy intake components
any foods that has calories: carbs, protein, fat, alcohol
energy expenditure components
- basal metabolism
- thermic effect of food (TEF)
- physical activity
- thermogenesis
thermogenesis
minor form of energy output (shivering, fidgeting)
BMR
basal metabolic rate = minimum amount of energy required for body functions when you’re resting
this is the LARGEST component of energy expenditure (60-70%)
increase BMR
- muscle mass
- body temp
- stress hormones
- thyroid hormones
- caffeine, tobacco
- recent exercise
decrease BMR
- hypothyroidism
- restricted calorie intake
- low muscle mass & body surface area
- aging declines 1-2% each decade after 30
RMR
resting metabolic rate: used if a person isn’t fasting or rested
about 6% higher than the BMR
BMR & RMR units
number of calories burned per hour
women = 0.9 calories/kg per hour
men = 1.0 calories/kg per hour
factors influencing body weight & composition
genetics & environment
physical activity and energy expenditure
most variable component of energy expenditure
increases kcal needs by about 25-40% (can be higher/lower)
TEF
thermic effect of food (digestion, absorption, metabolism) accounts for 5-10% of kcal
highest for protein
influenced by food composition & meal size
direct calorimetry
estimates energy expenditure by measuring amount of heat released by body
idea = similar to bomb calorimeter (where they burn food) but this time a PERSON’S heat release is measured by putting them in a chamber surrounded by water
expensive, complicated, not often used
adaptive thermogenesis
contributes a SMALL amount to expenditure
triggered by cold, overfeeding, trauma, starvation
indirect calorimetry
collects air expired during a certain time period
considers amount of oxygen consumer and CO2 products
doubly-labeled water also used
EER
Estimated Energy Requirements = equations based on evidence gathered thru direct & indirect calorimetry
EER factors
energy needs are based on:
- weight
- height
- sex
- age
- activity level
hunger
physiological drive to find/eat food
controlled by organs, hormones, & nervous system
appetite
psychological drive to eat
impacted by EXTERNAL factors
satiety
feeling of fullness following consumption of food
regulated by hypothalamus
satiation
causes us to stop eating
happens because of secretion of hormones during digestion
promoted by:
- sensory aspects of food
- knowledge food has been consumed
- chewing
- expansion of stomach & intestines
- effects of digestion, absorption, metabolism
- decrease in ghrelin
ghrelin
hormone that acts in the hypothalamus
promotes food intake: increases appetite, smell sensitivity, energy storage
leptin
hormone that acts in the hypothalamus
signals brain to decrease food intake
rises when body fat increases (secreted by adipose tissue
long-term satiety
promoted by body composition (amount of body fat)
satiety process
hours after eating, macro levels in the blood begin to fall
- body begins to use stored energy
- satiety signals diminish
- cortisol & ghrelin stimulate appetite
assess weight status
current recommendations say to evaluate:
- total body fat
- location of body fat
- weight-related medical complications
BMI
Body Mass Index, preferred height-to-weight standard
BMI benefits
- linked to longevity
- easy to assess
- applies to men & women
- accurate for MOST people
BMI exceptions
not appropriate for:
- children
- teens
- older adults
- pregnant/lactating women
- people under 5’
- muscular people
body composition methods
- underwater weighing
- air displacement
- skinfold thickness
- bioelectrical impedance (electrical current sent through body)
- dual energy x-ray absorptiometry (DXA) = MOST accurate
body fat levels
men: 8-24%
women: 21-35%
healthy weight
body weight that doesn’t increase risk of weight-related health problems or diseases
realistic healthy weight
a RANGE: depends on gender, height, muscle mass
achieved & sustained without restriction
android obesity
abdominal obesity = large waist circumference
associated with increased health risk
android obesity risk factors
- male
- high glycemic diets
- high alcohol consumption
- smokers
android obesity diseases
increased risk of:
- CVD
- hypertension
-T2DM
