HN&F 171 CH 8

energy balance

energy in = energy out

* imbalance causes weight changes

positive energy balance

Energy intake exceeds energy expenditure and results in weight gain

− Desired during growth stages: Pregnancy, Infancy, Childhood, Adolescence

negative energy balance

Energy intake is less than energy expenditure and weight loss occurs

− Desired in adults when body fatness exceeds healthy levels

does not

Aging _ cause weight gain

− It stems from a pattern of excess food intake coupled with limited physical activity and slower metabolism

food composition

1. Amount of energy in food or beverages can be estimated using nutrient databases or software • Physiological fuel value
2. Indirect measure of energy released can be estimated • Measures oxygen consumed

appetite

stimulated by sight, smell, thought, or taste of food

hunger

stimulated by absence of nutrients in blood

satiation

signal to stop eating (aka fullness, short term feeling)

− Protein and high fiber foods are very satiating

satiety

long term suppression of hunger between meals

− Fat promotes satiety

Overriding hunger and satiety

Stress eating

External cues

Time of day, availability, sight, taste of food

Environmental influences

Large portion sizes, food availability

disordered eating

Binging or ignoring hunger cues

3 main purposes the body uses energy

• Basal metabolism

• Physical activity

• Digestion, absorption, and processing of ingested nutrients (Thermic effect of food)

basal metabolism

• Activities to keep the body functioning (breathing, heart beating, nervous system functioning, etc.)

o Varies based on weight, lean tissue\*, age, and more

• Quantified by *basal metabolic rate (BMR)* or*resting metabolic rate (RMR)*

BMR

The minimum amount of energy expended to keep you alive while fasted and rested

RMR

used when not fasted or rested

factors that **increase** BMR

• Greater muscle mass

• Larger body surface (height and/or weight)

• Male gender

• Higher body temperature

• Higher than normal secretions of thyroid hormones

• Growth stages

• Caffeine and tobacco use

• Recent exercise

factors that decrease BMR

• Lower than normal secretions of thyroid hormones

• Restricted calorie intake

• Fasting/starvation

• Malnutrition

• Less body surface area

• Low muscle mass

physical activity (energy expenditure)

• Voluntary muscle movement

• Most variable and readily influenced component

• Weight, lean muscle, and the type of activity impact the amount of energy needed

• Frequency, intensity, duration

▪ Structured exercise vs. active lifestyle choices – both count

thermic effect of food

o The amount of energy needed to digest, absorb, transport, store, and metabolize food

o Accounts for \~10% of energy intake

o Varies based on meal frequency, size, and macronutrient composition

o **Protein** is the highest

energy used by body

can be *measured* by:

• Direct or indirect calorimetry

• Measured heat production/oxygen consumption via machines

\
can be *estimated* based on:

• Height

• Weight

• Physical activity

• Age

gender

**Women** tend to have a **lower** BMR than **men** due to **less lean body mass/less body surface**

age

BMR declines during adulthood as lean body mass declines

physical activity

Levels of intensity for each gender

body comp and body size

− Height

− Weight

criterion of fashion

− Judge ideals for body weight by appearance.

− Unrealistic ideals for body weight, especially for women

criterion of health

− Need enough body fat to meet basic needs but not too much as to lead to health risks

− Is achieved by good eating habits and regular physical activity

− Assessed via body composition too; defined as the proportions of muscle, bone, fat, and other tissue that make up a person’s total body weight

materials body is composed of

1. Body Fat
2. Lean Mass
3. Bone
4. Water

Determining if a person’s body weight is healthy

1. Determining the body mass index (BMI)
2. Assessing the pattern of fat distribution
3. Measuring body composition

BMI

Measure of relative weight for height

▪ Not a measure of body composition

▪ Not appropriate for everyone

healthy weight

**BMI = 18.5 to 24.9**

▪ Typically results in normal health measures

underweight

**BMI <18.5**

− Too little body fat to maintain health

overweight

**BMI 25 to <30**

− May have moderate amount of excess body fat

obese

**BMI > 30**

\- Health risks associated with too much body

body fat and distribution

− Men: __**8% to 24%**____;__ over 24% considered obese

− Women: __**21% to 35%**____;__ over 35% considered obese

▪ Need more body fat because of reproductive functions

how to measure body fat

− Underwater weighing

− Air displacement (BodPod)

− Bioelectrical impedance

− Skinfold measures

− DXA

* Most accurate

visceral fat

• Central/abdominal obesity

• Significantly contributes to heart disease, and diabetes

healthy

In _ weight people, small amounts of fat is stored around the organs of the abdomen

over

In _ weight people, excess abdominal fat around abdomen increases the risks of diseases

Subcutaneous fat

Stored around hips and thighs

assessing fat distribution

health risks seen when waist circumference is:

• >40 inches in males

• >35 inches in females

Risks associated with being underweight

− Fighting against wasting diseases

− Menstrual irregularities and infertility

\- Osteoporosis and bone fractures

risks of overweight and obesity

− Cardiovascular disease

▪ Elevated blood cholesterol and hypertension

▪ Central obesity

• Diabetes—type 2

▪ Central obesity

Weight gains and body weight