Chapter 8: Energy Balance and Body Composition

Energy balance

when energy in = energy out

what happens when one consumes more food energy than expended

weight gain

what happens when one consumes less food energy than expending

weight loss

1lb of body fat is equal to how many kcals eaten in excess

3500 kcals

what is safe weight loss per week

1/2lb - 2 lb

which kind of weight loss is maintained better

gradual and slow

what does rapid weight loss take off

some fat, large amounts of fluid and some lean tissue

bomb calorimeter

an instrument that measure the heat energy released when foods are burned, thus providing an estimate of the potential energy of the foods

kcals

units of heat energy

what is generated in the bomb calorimeter

carbon dioxide and water

what is more efficient the body or a calorimeter

calorimeter, values are corrected mathematically

what can food energy values be determined by

- direct calorimetry
- indirect calorimetry

direct calorimetry

measures the amount of heat released

indirect calorimetry

measures the amount of oxygen consumed and CO2 expelled

Hunger

- the uncomfortable sensation caused by a lack of food that initiates food-seeking behavior
- the physiological drive for food; is triggered by chemical messengers originating and acting in the brain

what can influence hunger

- nutrients in the bloodstream
- the size and composition of the preceding meal
- customary eating patterns
- climate

why would the hunger response adapt

to accommodate changes in food intake

what are normal signs of hunger

- difficulty concentrating
- feeling faint
- headache
- irritability
- lightheadedness
- mild gurgling or gnawing in stomach

what are signs the initiate or delay eating?

- hunger
- appetite
- satiation
- satiety

appetite

the integrated response to the sight, smell, thought or taste of food that initiates or delays eating

satiation

the feeling of satisfaction and fullness that occurs during a meal and halts eating; triggered by stretched stomach receptors, release of GI hormones in small intestine and stimulation of nerves

satiety

the feeling of satisfaction that occurs after a meal and inhibits eating until the next meal; determines how much time passes between meals

signals that trigger or suppress eating

- boredom/anxious
- response to stress (positive or negative)
- environmental influences
- cognitive influences
- eating disorder

how do environmental influences trigger or suppress eating

large portion sizes, favorite foods, being presented with a variety of foods

how do cognitive influences trigger or suppress eating

perceptions, memories, intellect and social interactions

how do eating disorders trigger or suppress eating

anorexia nervosa

how to sustain satiation and satiety

- consume foods rich in protein and complex CHO and low in fat
- eat slowly
- don't wait until you are famished to eat
- pay attention to how you feel
- watch portion sizes

how does consuming food rich in protein and complex CHO and low in fat help prevent overindulging

protein is most satiating (having the power to suppress hunger and inhibit eating); foods rich in complex CHO and fibers also help fill the stomach and extend satiety; high-fat foods have a weak satiating effect; lead to over consumption (offer flavor, enticing people to eat more)

how does eating slowly help prevent overindulging

allows stretch receptors in stomach to signal brain that you are full

how does not waiting until you are famished to eat help prevent overeating

do not have large spaces between meals; consume healthy snack throughout day

how does paying attention to how you feel help prevent overeating

to avoid stress eating

how does watching portion sizes help prevent overeating

buy only single servings of foods you crave; to feel satisfied choose larger portions of high-protein and high-fiber foods instead of small portions of high-fat foods

thermogenesis

generation of heat

how is thermogenesis used in nutrition

used as an index of how much energy the body is expending

total energy a body expends reflects three main categories of thermogenesis:

- basal metabolism
- physical activity
- thermic effect of food

adaptive thermogenesis

includes adjustments in energy expenditure related to changes in environment (extreme cold and heat, overfeeding, trauma and stress)

basal metabolism

the energy needed to maintain life when a body is at complete digestive, physical and emotional rest

examples of metabolic actives for basal metabolism

- maintain body temperature
- lungs breathing
- heart beating

what is the largest component of energy expenditure

- basal metabolism
- 2/3 of the energy the average person spends in a day

basal metabolic rate (bmr)

the rate at which the body spends energy for maintenance activities

resting metabolic rate

the measure of energy output when a person is at rest in a comfortable setting, but with less stringent criteria for recent food intake and physical activity; is slightly higher than BMR

physical activity

voluntary movement of the skeletal muscles and support system; muscles need extra energy to move and heart and lungs need extra energy to deliver nutrients and oxygen and dispose wastes; energy needed for an activity depends on muscle mass, body weight and activity (including type, duration, frequencey and intensity)

thermic effect of food

estimation of the energy required to process food (digest, absorb, transport, metabolize and store ingested nutrients); depends on meal size, frequency and composition

which factors affect BMR

- age
- height
- growth
- body composition
- gender
- fever and stress
- environmental temp
- fasting/starvation/malnutrition
- hormones
- smoking
- caffeine
- sleep

how does age affect BMR

lean body mass diminishes, slowing BMR

how does height affect BMR

BMR is higher in tall people

how does growth affect BMR

BMR is higher in children/pregnancy

how does body composition affect BMR

more lean tissue = higher BMR

how does gender affect BMR

BMR is higher in males

how does fever + stress affect BMR

raises BMR

how does Environmental Temp affect BMR

heat/cold raise BMR

how does fasting/starvation/malnutrition affect BMR

lowers BMR

how do hormones affect BMR

thyroid hormone increases or decreases BMR

how does smoking affect BMR

increases energy expenditure

how does caffeine affect BMR

increases energy expenditure

how does sleep affect BMR

BMR is lowest sleeping

body composition

the proportion of muscle, fat and other tissues that make up a person's total body weight

what defines a healthy body weight

- weight within suggest range for height
- fat distribution pattern associated with low risk for illness and premature death
- medical history that reflects absence of risk factors associated with obesity
- a person needs enough body fat to meet basic needs but not os much to incur health problems

BMI

the index of a person's weight in relation to height; not body composition

how to calculate BMI

(actual weight (in lbs)/ height (inches) squared ) x 703

underweight BMI

less than 18.5

healthy weight BMI

18.5-24.9

overweight BMI

25-29.9

mild obesity BMI

30-34.9

moderate obesity BMI

35-39.9

Severe obesity BMI

over 40

% body fat

amount of body fat

normal body fat %f in men

18-27

normal body fat % in women

23-24

male athlete body fat %

7-16

female athlete body fat %

15-22

what to know about being below a certain threshold for body fat

- faltered hormone synthesis
- infertility
- depression
- abnormal hunger regulation
- inability to keep warm

upper body fat

intra-abdominal fat or visceral fat; android or "apple" shaped; fat stored within the abdominal cavity in association with the internal abdominal organs

what is upper body fat typically associated with

central obesity; fat is more mobile and moves into vessels

what diseases are associated with upper body fat

- increased risk of heart disease
- stroke
- diabetes
- hypertension
- gallstones
- cancer

what diseases are associated with lower body fat

less susceptible to health problems

waist circumference

an anthropometric measurement used to assess a person's abdominal fat; provides information on location of body fat

what waist circumferences are health risks in men and women

men >40, women >35

what tends to increase fat accumulation in the stomach

smoking and drinking

waist to hip ratio

also assess abdominal obesity; divides wasitline measurement in inches (around belly button) by hip measurement in inches (largest circumference)

what waist to hip ratio is a health concern for men and women

men >.90 and women >.80

methods used to determine body composition (body fat %)

- skinfold measurement
- bioelectrical impedance (BIA)
- total body electric conductance (TOBEC)
- hydrostatic weighing
- air displacement plethysmography

skinfold measurements

measures body fat and indicates body calorie reserve (fat distribution is 50% subcutaneous and 50% visceral)

where is the most common site for skinfold measurement

triceps

bioelectrical impedance (BIA)

- electrical current passed through the body
- current is opposed by nonconducting tissues (fat) and transmitted by conducting tissues (electrolytes dissolved in water in fat free tissues)
- resistance to current is measured

total body electric conductance (TOBEC)

- person sits in an electromagnetic field; electrolytes within fat free mass conduct electricity
- degree to which person disrupts field depends on quantity of conducting material (fat free mass) in person; lower inductance = more body fat

hydrostatic weighing

- a person is placed in an underwater weighing tank
- the volume of the body (determined by the displacement of water) and height can determine density and fat free mass
- body fat is determined by the difference between body mass and fat free mass

hydrostatic weighing - a person with more dense (muscle)

less water is displaced

hydrostatic weighing - a person with less dense (fat)

more water is displaced

air displacement plethysmography

-based on the same whole-body measurement principle as hydrostatic weighing
- a person sits inside a chamber instead of becoming immersed in water
- computerized sensors determine the amount of air displaced by the persons body
- testing using the BOD POD has been reported to be the most accurate and convenient indirect method of body composition analysis

what are the risks of being underweight

- vitamin/mineral deficiencies
- unable to preserve lean tissue during wasting disease such as cancer or a digestive disorder
- menstrual irregularities/infertility
- osteoporosis

health risks associated with being overweight/obese

- cardiovascular disease
- diabetes
- inflammation and the metabolic syndrome
- cancer
- hypertension
- sleep apnea
- osteoarthritis
- gallbladder disease
- kidney stones
- respiratory problems
- psychological/social effects
- complication in pregnancy/surgery

cardiovascular disease

central obesity raises the risk of heart attack and stroke das much as the three leading risk factors (high LDL cholesterol, hypertension, and smoking)

diabetes

type II - 3x more likely; central-body fat cells are larger and more insulin-resistant than lower-body fat cells

Inflammation and the Metabolic Syndrome

accumulation of fat in adipose tissue (especially in abdominal region), muscles and liver cause a cluster of symptoms which may include insulin resistance, low HDL, high triglycerides and high blood pressure which increases risk of chronic disease

lower body fat

subcutaneous fat; gynoid or “pear” shaped; fat stored directly under the skin; fat around the hips and thighs; fat is less mobile