HLSC-2P92 Lecture 6: Energy Balance, Body Composition, and Physcial Acivity

Energy balance

Energy balance

- if a person maintains a healthy weight over time, the person is in energy balance

energy intake = energy expenditure

Healthy body weight

- appropriate for age, sex, and height
- maintained without constant dieting
- acceptable to you
- promotes good eating habits and allows for regular physical activity

Energy intake

Energy intake = energy (kcal) provided by foods and beverages

Energy expenditure

Energy expenditure = energy (kcal) expended at rest and during physical activity

What is energy used for?

- basal metabolism,
physical and voluntary activities and for thermic effect of food

Basal metabolism

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

- energy expended to maintain basal, or resting, functions of the body (e.g. respiration, circulation)

- supports the body's work that goes on all the time without the person's conscious awareness

- 50-65%

Basal metabolic rate (BMR)

- rate at which person expends energy
- varies from person to person
- slowest when person is asleep
- measured when the person is awake, but lying still, in a room with comfortable temperature after a restful sleep and an overnight (12-14 hours) fast

Resting metabolic rate (RMR)

- similar measure of energy output; a measure of the energy use of a person at rest in a comfortable setting

- less stringent criteria for recent food intake and physical activity

- slightly higher than BMR since it accounts for additional low-effort daily activities on top of basic body functions

Factors that influence BMR

- age: lean body mass diminishes with age, slowing BMR
- height: tall, thin people have high BMR
- growth: children and pregnant women have high BMR
- body composition (sex): the more lean tissue; the higher the BMR (males have a higher BMR than females). The more fat tissue, the lower the BMR
- fever: raises BMR
- stresses: raises BMR
- environmental temp: heat and cold raise BMR
- fasting/starvation: lowers BMR
- malnutrition: lowers BMR
- hormones: thyroxin speed up or slow down BMR, premenstrual hormones slightly raise BMR
- smoking: increases EE
- caffeine: increases EE
- sleep: BMR is lowest when sleeping

What factor is the main contributor to BMR?

body composition

When is the BMR lowest?

sleeping

Physical activity

- voluntary movement of skeletal muscles and support systems above basal metabolism

expenditure

- most variable part of energy output

- 30-50%

Physical activity includes three components:

- duration
- frequency
- intensity

Thermic effect of food

- an estimation of the energy required to process food (digest, absorb, transport, metabolize, and store ingested nutrients)
- as food is ingested, cells become active; cells require extra energy for digestion, absorption and metabolism of food; cellular activity produces heat and is known as the thermic effect of food
- proportional to energy content of mixed meal (~10%)

Example of thermic effect of food

for example if someone eats a 850 kcal dinner, about 85 kcal are spend for digestion, absorption and metabolism of the dinner

Direct calorimetry

- measures the amount of heat the body releases
- rarely used due to time and expense
- requires 12 hours of fasting
- requires an environmentally controlled room or chamber
- 1 kal = amount of energy (heat) required to raise 1 kg (1 L) of water by 1 C at sea level

Indirect calorimetry

- estimates energy expenditure based on O2 consumption and CO2 release
- less expensive and more accessible

Measuring total energy expenditure

TEE = (BMR or RMR) + dietary thermogenesis + physical activity

What is the gold standard for measuring TEE?

doubly labeled water

Factors that influence energy expenditure

- gender
- growth
- age
- physical activity
- body composition and body size
- varies between individuals

Weight gain

energy intake > energy expenditure

Weight loss

energy intake < energy expenditure

Underweight

too little body fat to maintain health

Overweight

having a moderate amount of excess body fat

Obesity

excess of body fat that adversely affects health

Evaluating body weight

- a person's actual weight is not the only factor to consider

- determining if a person's body weight is healthy should include:

- body mass index (BMI)

- body composition

- pattern of fat distribution

Body Mass index

expresses the ratio of a persons weight to the square of their height and used to define underweight, overweight, and obese. does not identify how much of weight is fat or where fat is located

= weight (kg) / height (m)2

Healthy weight BMI range

18.5-24.9

Overweight BMI range

BMI between 25 and 29.9, can lead to obesity

Obesity BMI range

BMI over 30
includes clinically obese

Health risks of overweight and obesity

- hypertension
- increased blood pressure
- high blood lipids
- fatty liver disease
- some cancers
- sleep apnea
- complications in pregnancy and surgery

Underweight BMI range

BMI below 18.5
increased risk of infections and illness; can even be fatal,
can be just as unhealthy as overweight

Limitations of body mass index

- Under the age of 18 years
- Pregnant or nursing
- Over age 65 years
- Certain ethnic and racial groups
- High in muscle mass

Body composition

provide an assessment of:

lean body mass

percent body fat.

DEXA

estimates lean tissue, bone, mineral and fat mass

Hydrostatic (underwater) weighing

determination of bone density by comparing the body's weight on land and in water or by measuring the body's volume

Air displacement plethysmography

measurement of body density and bod pod system

Skinfold thickness

estimates body density based on subcutaneous fat (using calipers)

Bioelectrical impedance analysis (BIA)

measurement of total body water and fatness. measures magnitude of an electrical current passed through the body, electrical conductivity higher in lean tissues than fat tissue

% Body fat recommendations

13 to 21 percent for men
23 to 31 percent for women

Fat distribution pattern

measured by waist-to-hip ratio and waist circumference,
look at fat patterning

Pear-shape

lower body
subcutaneous/peripheral fat
no increased risk for chronic diseases

more common in women

Apple shaped

upper body
abdominal/visceral (central) fat
increased risk for chronic diseases (e.g. heart disease, stroke, diabetes, hypertension, and some types of cancer)

more common in men

Risk (waist-to-hip ratio) (waist circumference/hip circumference)

> 0.9 for men
> 0.8 for women

Gaining or losing weight

depends on:

1. energy balance = energy intake vs. energy expenditure

2. genetic factors (25%)

3. physiological factors

Genetic factors

- thrifty gene theory
- set-point theory

Thrifty gene theory

- evolved from hunter-gatherers who went without food for extended periods of time; genes were adopted to store energy
- some people possess a gene that allows them to expend less energy than other people
- modernization has allowed us to expend less energy (energy conservation) while taking in more

Set point theory

- proposes that body weight is physiologically regulated
-body adapts to maintain its preferred weight
- increase energy intake, increase BMR;
- decrease energy intake, decrease BMR

Physiological factors

- hunger and satiety
- proteins/Hormones such as:
-leptin
-ghrelin

Leptin

- hormone produced by fat cells in proportion to the amount of fat stored

gain in body fat stimulates production of _____

- suppresses appetite

- increases energy expenditure

fat loss decreases ______ production

- increases appetite

-decreases energy expenditure

What is the purpose of leptin?

- appetite suppressor
- stored and secreted by fat cells, is considered to be the master regulator of hunger
- when you eat a meal, it is releases and sends a signal to your brain to let you know you are full and to stop eating

Ghlerin

- protein/hormone synthesized and secreted primarily by stomach cells
- promotes positive energy balance by stimulating appetite and promoting efficient energy storage; it signals the hypothalamus of the brain to stimulate appetite and food intake
- triggers desire to eat
- blood levels typically rise before and fall after a meal

What is the purpose of ghrelin?

- appetite stimulator
- released by stomach cells and when elevated, sends a signal to your brain letting you know you are hungry

Social factors

- family or cultural traditions
- holidays and celebrations
- easy access to high-fat foods
- less physically active lifestyles
- societal expectations of the "perfect" body

Healthy body weight

healthy body weight change requires:
- gradual change in energy intake
- strategize around two goals:
1. change body weight by 5-10% over 6 month period
2. maintain changed body weight over a period of years

Effective weight loss diet should include:

- following recommended servings and portion sizes; difficult to achieve nutritional adequacy with fewer than 1200 kcalories per day
- eat smaller, more frequent meals
- eat before you become extremely hungry
- eat more fresh and less processed foods
- eat foods with a low energy density and a high nutrient density (e.g. fruits and vegetables)
- choose whole grains and fiber-rich vegetables
- choose fats sensibly; include enough unsaturated oils
- limit intake of added sugars and alcohol
- drink adequate water; replacing energy-dense beverages with water could save a person up to 15 pounds a year; water helps the GI tract adapt to a high-fiber diet

Fad Diets

- many do not offer safe and effective plan for weight loss
- no credible research needed to publish
- may exclude or restrict healthful foods
- nutrient intakes suffer
- may offer some short-term weight loss success
- difficult to sustain restrictive behaviors

Tips for identifying FAD Diets

- guarantees an unrealistic outcome in an unreasonable time period. "loss 10 pounds in 2 weeks"
- specifies a proportion for the energy nutrients that falls outside the recommended ranges—carbohydrate, 45 to 65 percent; fat, 20 to 35 percent; and protein, 10 to 35 percent

Effective weight gain diet should include:

- eating 500 to 1,000 extra kcal/day
- maintaining a balanced diet
- eating frequently throughout the day (at least 3 meals a day and snacks in between)
- choose energy-dense foods most often
- drink calorific drinks e.g. milk
- avoiding tobacco products which depress appetite and increase BMR

Healthy body weight behavior

healthy body weight change requires:

- gradual change in energy intake

- application of behavioral modification techniques

- becoming aware of behaviors

- making small changes

- adopting new ways of thinking

- sound emotional support

- regular and appropriate physical activity

Physical activity is:

any muscle movement that increases energy expenditure

Leisure time physical activity

- any activity unrelated to a person's occupation (ex: hiking, biking)

- includes exercise - purposeful, planned physical activity; planned, structured, and repetitive bodily movement that promotes or maintains physical fitness

Benefits of physical activity

- improves body composition (more lean tissue), bone density, and immune system
- reduces the risk of
1. cardiovascular disease
2. obesity
3. type 2 diabetes
4. osteoporosis
5. colon cancer

Physical fitness

- the ability to meet routine physical demands
- the characteristics that enable the body to perform physical activity
- state of being created by the interaction between nutrition and physical activity
- nutrition and physical activity influence each other
- working body demands nutrients
- physical activity regulates use of fuels and shifts body composition toward leanness
- physical fitness depends on physical activity, or exercise

Physical fitness includes:

- cardiorespiratory fitness
- musculoskeletal fitness
- flexibility
- body composition
all encompass: endurance, flexibility and strength

Physical fitness program includes:

- meets your personal goals

- is fun

- warm up and cool down period

- includes variety and consistency

- appropriately overloads the body

- integrates proper nutrition

Overload principle

additional physical demands placed on the body to improve fitness
- too much physical exertion is NOT recommended
- FIT principle can be used to determine appropriate overload

FIT principle includes:

frequency, intensity, time

Frequency

the frequency of physical activity varies with fitness goals

Intensity

determining proper intensity may be based on maximal heart rate

Time

whether the total activity time is an accumulation of activities or completed all at once

Adults 18-64 years

150 minutes of moderate-to-vigorous physical activity per week

0-4 years

180 minutes of physical activity at any intensity spread throughout the day

5-11 years

60 minutes of moderate-to-vigorous-intensity physical activity daily

12-17 years

60 minutes of moderate-to-vigorous-intensity physical activity daily

65 years and older

150 minutes of moderate-to-vigorous-intensity aerobic physical activity per week

Weight loss - physical activity

- weight gain prevention and augmented weight loss occur with at least 2 hours and 30 minutes (150 minutes) per week of at least moderate-intensity physical activity

- greater weight loss and improved weight maintenance after weight loss occur with more than 4 hours and 10 minutes (>250 minutes) per week of at least moderate-intensity physical activity

- both aerobic (endurance) and muscle-strengthening (resistance) physical activities are beneficial, but kcalorie restriction must accompany resistance training to achieve weight loss

Factors influencing number of kcalories expended

- body weight
- duration of activity
- intensity of activity

Weight loss physical activity

- BMR is elevated in the hours after vigorous physical activity
- engaging in daily vigorous physical activity develops more lean tissue
(more metabolically active than fat tissue)
- physical activity helps control appetite. appetite is suppressed immediately after an aerobic workout

Adenosine triphosphate (ATP)

- the energy carrying molecule in the body

ATP must be generated continuously since muscles store only enough ATP for 1

- 3 seconds of activity

Creatine phosphate (CP or PCr)

- stores some energy that can be used to make ATP

- stores enough energy for 3 to 15 seconds of maximal physical effort (e.g. 100m sprint)

Fuel for physical activity

- after creatine phosphate, carbohydrates and lipids are the next source of energy for the production of ATP
- proteins are not used extensively as fuel source for physical activity

The active body's use of fuels

- glucose from carbohydrate primary fuel
- also fatty acids and amino acids to lesser extent
- muscles always use a mixture of fuels
- muscle glycogen fuels early minutes of activity
- as activity continues, messenger molecules, including the hormone epinephrine, flow into the bloodstream to signal the liver and fat cells to release their stored nutrients, primarily glucose and fatty acids

Glucose use during activity:

- glucose stored by liver and muscles as glycogen
- liver can produce glucose from fragments of other nutrients
- glycogen stores retained by muscles
- diet effects glycogen storage and use
- body constantly uses and replenishes glycogen
- the more dietary carbohydrate, the more glycogen stored in muscle
- supports physical activity longer

Activity intensity affects glycogen use

- body stores far less glycogen than fat

- how long glycogen stores last depends on diet and intensity of activity

- moderate activities use glycogen slowly (aerobic metabolism)

- intense activities use glycogen quickly (anaerobic metabolism)

Activity duration affects glycogen use

- early in activity, muscles rely on own stores of glycogen

– as muscles stores deplete, liver supplies additional glycogen

- after about 20 minutes of moderate exercise, less glucose and more fat used for fuel

- glycogen depletion occurs after about two hours of vigorous exercise

Carbohydrates

- high-___________ diet about 8 grams per kilogram of body weight or about 70 percent of energy intake
- take glucose periodically during activities lasting one hour or more
- eat __________-rich foods (about 60 grams) immediately after activity
- train muscles to store as much glycogen as possible

Fat use during physcial activity

- recommendations for athletes
- 20-35 percent of total intake from fat
- if restricted below 20 percent, may not consume adequate energy and nutrients
- body fat stores
can total 70,000 kcal or more
- glycogen stores limited to 2,000 kcal or fewer

Intensity and duration affect fat use

- as intensity increases, fat contributes less to fuel mixture
- fat broken down for energy only by aerobic metabolism
- oxygen must be abundantly available
- longer duration results in signal to break down stored triglycerides
- freeing fatty acids into blood

Protein

- important for building and maintaining muscle mass, precursor for gluconeogenesis during exercise, aids in recovery from exercise

Calcium

- builds and maintains bones, aids with muscle contraction and nervous system function
-RDA is 1000mg/day for women 18 to 50 years old and men 18 to 70 years old

Iron

- transport of oxygen

- absorption increased w/ vitamin C

-female athletes prone to iron deficiency and especially endurance athletes

causes:

- insufficient dietary intake

- high ______ losses through menstruation

- increased losses associated with haemolysis, sweating, gastrointestinal bleeding and exercise induced acute inflammation

- adolescent female athletes consuming vegetarian diet also vulnerable

Diets for physically active people

- diet high in carbohydrate, moderate in fat, and adequate in protein is sufficient
- nutrient-dense foods (give maximum vitamins and minerals for the energy provided)

Examples of nutrient-dense snacks for active people

- almonds
- low-fat greek yogurt
- low-fat milk or chocolate milk
- popcorn