Ch7 - Energy Balance and Weight Management

ideal body weight (IBW)

weight that can be maintained without dieting or training and that and that the person feels good at; appropriate for your age, maintained without constant dieting, acceptable to you, based on family history of body shape and weight, promotes good eating habits and allows for physical activity

factors for determining healthy body weight

body mass index, body composition, pattern of fat distribution

body mass index (BMI)

ratio of a persons weight to their height squared

limitations to BMI

does not distinguish between fat and muscle mass, various ethnicities, sex, elderly; not accurate for people with disproportionate height, older adults, and pregnant/lactating women

body composition

the ratio of body fat to lean body tissue, including muscle, bone, water, and connective tissue such as ligaments, cartilage, and tendons

what is an acceptable BMI range

18.5-30

underweight BMI

normal BMI

18.5-24.5; least disease risk

overweight BMI

25.0-29.9; increased disease risk

class I obese BMI

30.0-34.9; high disease risk

class II obese BMI

35-39.9; very high disease risk

class III obese BMI

>40; extremely high disease risk

how to calculate BMI

weight (kg) / height (m^2)

underweight

having too little body fat to maintain health

overweight

having a moderate amount of excess body fat

obesity

having an excess of body fat that adversely affects health

fat mass

adipose tissue mass

fat free mass

muscle, organs, bone, water, etc. mass

healthy body fat range

Men: 8-20%

Women: 21-33%

underwater weighing

A method of estimating total body fat by weighing the individual on a standard scale and then weighing them again submerged in water. The difference between the two weights is used to estimate total body volume;

accurate & noninvasive, participant burden, not appropriate for children and frail individuals

BODPOD

A device used to measure the density of the body based on the volume of air displaced as a person sits in a sealed chamber of known volume;

more accurate and convenient than underwater weighing

Dual Energy X-ray Absorptiometry DXA

method to assess body composition that uses very low-dose beams of x-ray energy to measure total body fat mass, fat distribution pattern, lean mass, and bone density; current gold standard for body comp assessment

bioelectrical impedance analysis (BIA)

A method of assessing body composition by running a low-level electrical current through the body; estimates body fat by measuring resistance of current; inexpensive & quick; affected by the amount of water in the body

skinfold measurements

A method to estimate body fat by measuring with calipers the thickness of a fold of skin and subcutaneous fat; difficult to perform and less accurate in obese and elderly

how is the risk associated with visceral fat calculated

measuring waist circumference

dangers of high visceral fat

associated with higher incidence of heart disease, high BP, stroke, diabetes

waist circumference not associated with greater health risk

less than 102cm for men

less than 88cm for women

varies among ethnicities

visceral fat

fat located around major organs; also called intra-abdominal fat

subcutaneous fat

fat located under the skin

adipose tissue

collection of fat cells

apple shaped fat pattern

rounded fat pattern in upper body; increased risk for chronic disease

pear shaped fat pattern

pear-like fat pattern in the lower body; no significant increased risk for chronic disease

fat distribution patterns

apple-shaped or pear-shaped

in whom is visceral fat storage more common

men & women after menopause

effects of estrogen on visceral fat deposition

protects against visceral fat deposition

factors that increase fat deposition

stress, tobacco, alcohol, physical activity

energy balance

when energy consumed equals energy expended; body weight is not changing

negative energy balance

energy intake is less than output; weight loss

positive energy balance

energy intake is more than output; weight gain

kcal

measure of amount of energy supplied to or expended by the body

how is energy measured

kilocalories or kilojoules

obese BMI

>30

glycogen

Storage form of glucose; in liver and muscle; fill when carbohydrate is adequate; enough energy for about 24hr of glucose

glucose/free fatty acids

primary fuels of aerobic system that float freely in body fluid

triglycerides

an energy-rich compound made up of a single molecule of glycerol and three molecules of fatty acid; found in adipose tissue; most energy rich energy source

adipocytes

fat cells developed in adolescents that change in size depending on amount of triglycerides

protein

An organic compound that is made of one or more chains of amino acids; found in muscle cells; 2nd most energy rich source

energy storage sources

glycogen, glucose/free fatty acids, triglycerides, protein

energy

capacity to do work

what does the body use energy for

move muscles, organ function, transport/build/breakdown/build molecules

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

what is body weight determined by

energy balance

energy intake

kcal from food

energy expenditure

kcal expended at rest and during physical activity

energy sources in diet

carbohydrates, lipids, protein, alcohol

components of energy expenditure

basal metabolic rate, thermic effect of food, energy cost of physical activity

Basam Metabolic Rate (BMR)

energy expenditure for basic bodily functions; 60-70% of total energy

Total Energy Expenditure (TEE)

the sum of the energy used for basal metabolism, activity, processing food, deposition of new tissue, and production of milk

thermic effect of food (TEF)

The energy required to digest, absorb, and process nutrients that are consumed; 5-10% of total energy

physical activity energy cost

energy used in daily activities and planned exercise; 20-35% of total energy

factors that affect BMR

amount of lean tissue, height, age, gender, fasting, growth, thyroid hormone, medications

when is RMR measured

Awake, lying down, at a constant temperature, 12 hours after their last meal (usually in the morning)

resting metabolic rate (RMR)

The energy required to maintain essential body processes at rest.

how does fasting affect BMR

reduces BMR by up to 15% as an energy saving mechanism

respiratory quotient

ratio of CO2 produced to O2 consumed; used to calculate BMR

when is RQ = 1

100% carbohydrate oxidation

when is RQ = 0.7

100% fat oxidation

when is RQ = 0.8-0.9

100%protein oxidation

when is RQ = 0.8

mixed diet

what affects TEF

amount of fat in food; high fat means more energy required to digest

what affects energy expended in physical activity

body size, intensity of exercise, exercise time

hierarchy of body energy

1. alcohol

2. protein

3. carbohydrate stores

4. carbohydrate energy

5. carbohydrate fat storage

6. fat energy

7. fat stores

intensity categories of activities

daily activities, moderate activities, vigorous activities

factors that affect food intake & weight change

childhood weight, behavioral/social factors, genetics, hormones, energy balance, pleasure, environmental influences, disease, emotional factors, metabolic influences

short term regulation of energy balance

regulating food intake from meal to meal

factors affecting short term energy regulation

hunger, satiation, appetite, satiety; triggered by signals from GI, levels of circulating nutrients, signals from brains

hunger

internal signals that stimulate the acquisition and consumption of food

satiation

feeling of fullness that determines length of meal

satiety

feeling of fullness that determines time between meals

appetite

physiological desire for food driven by behaviour

long term energy balance regulation

regulating the amount of body fat

body system factors affecting food intake

hormones from GI, nerves in GI, blood nutrient levels

social influences affecting food intake

peer pressure, culture, religion, societal norms

grelin

A hunger-arousing hormone secreted by an empty stomach

how has fast paced lifestyle influenced our diet

meals are prepared in less time which means they often contain processed foods that are easy to make and ready to eat style

pleasure factors affecting food intake

taste, texture, odor

environmental factors affecting food inake

temp, availability of food

disease factors affecting food intake

diabetes, eating disorders, etc.

emotional factors affecting food intake

stress, boredom, perceptions/beliefs about food

metabolic factors affecting food intake

activity level, energy needs, pregnancy/breastfeeding

risk of a child being obese

10% if neither parents is obese, 50% if one parent is obese, 80% if both parents are obese

thrifty gene theory

proposes that a gene causes people to be energetically thrifty; they expend less energy than other people and therefore gain weight when food is plentiful; the actual gene has not been identified

set point theory

proposes that each persons weight stays within a small range (set point); the body compensates for changes in energy balance and keeps a persons weight at their set point; explains why dieting may not work long term

leptin

hormone produced by fat cells that causes reduced food intake, reduced weight, decreased body fat

leptin resistance

a condition in which higher-than-normal blood levels of the hormone leptin do not produce the expected physiological response; proportional to insulin resistance

ob gene

gene that codes for leptin; mutations can lead to increased food intake

how is leptin regulated

large adipocytes release more leptin to decrease energy intake and energy expenditure; vice versa for small adipocytes

ineffective unhealthy weight loss strategies

fasting, very low energy diets, fad diets, gimmicks

true test of weight loss strategy effectiveness

whether individuals maintain weight loss long term

fad diets

weight-loss plans that tend to be popular for only a short time; appeal to public fears of weight