Transcript Energy Balance

Energy Balance, Body
Composition & Weight
Management
Readings: Chapter 9
Energy Balance
• unbalanced energy budgets can lead to
weight gain or weight loss
• excess energy beyond body’s needs
increases fat storage
• too little energy results in degradation of
lean tissue to support energy needs
• both extremes have serious health
implications
Energy Balance
Maintaining weight means that:
ENERGY IN
ENERGY OUT
Figure 8-1, page 242
Energy Intake
Energy In = kilocalories from FOOD and DRINK
How do we determine how much energy food provides?
Bomb Calorimetry
 food is burned in an
insulated chamber
surrounded by water
 can measure:
a) heat produced
b) O2 consumed
Energy Intake
Limitations of Bomb Calorimetry
• more efficient than human body
Physiological Fuel Value = the number of
kilocalories the body derives from a food (less
than bomb calorimetry)
Based on Food Composition
• carbohydrates and protein provide 4 kcal/g,
fat provides 9 kcal/g and alcohol 7 kcal/g
Regulation of Energy Intake
Recall from introductory Lecture
• Hunger vs Appetite
• the physiological drive for food that
INITIATES food seeking behaviours
• influenced by factors such as:
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Sensory
Cognitive
Environmental
Health
• triggered by chemical messengers acting on
the HYPOTHALAMUS
• satiation
MORE SATIATING
boiled white potatoes
baked fish
oatmeal with milk
orange, apple
whole grain pasta
beefsteak, baked beans
popcorn, eggs
rice
white bread
snack chips, ice cream
chocolate bar
cake doughnuts
croissant
LESS SATIATING
Energy Expenditure
Thermogenesis
• the generation of HEAT
• used in physiology and nutrition studies
as an index of how much energy the
body is spending
Components of Energy Expenditure
• basal/resting energy expenditure
• energy of physical activity
• thermic effect of food
• adaptive thermogenesis
Physical
Activity
(25 – 35%)
Thermic
Effect of Food
(5 – 10%)
Basal/Resting
Energy Expenditure
(60 – 65%)
Basal/Resting Energy
Expenditure
• the energy needed to maintain life when
the body is at complete digestive,
physical, and emotional rest
• largest component of energy
expenditure
• measured as either basal metabolic rate
(BMR) or resting energy expenditure
(REE)
Estimating REE: Harris-Benedict
Equations
Male
66 + (13.7 x weight) + (5 x height) - 6.8 x age)
Female
655 + (9.6 x weight) + (1.8 x height) - (4.7 x age)
Example:
20 year old male, weight = 70 kg, height = 175 cm
= 66 + (13.7 x 70 kg) + (5 x 175) – (6.8 x 20)
= 66 + 959 + 875 – 136
= 1,764 kcal/day
Table 8-3, page 249; “How to”, page 250
Factors that Influence BMR
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increased lean body mass
growth and pregnancy
fever
thyroid hormone (thyroxin)
drugs such as caffeine,
nicotine, amphetamines
 height
 stresses (e.g. diseases)
 environmental temperature
(both heat and cold)
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increased age
increased body fat
sleep
malnutrition
starvation
Table 8-1, page 247
Energy of Physical Activity
• voluntary movement of the skeletal muscle
and support system
• most VARIABLE component of energy
expenditure
• amount of energy required for an activity
depends on:
– muscle mass
– body weight
– activity (intensity, duration, and frequency)
Table 8-2, page 248
Energy of Physical Activity
• can also estimate based on an activity factor
which is then multiplied by the BMR (or REE)
to estimate average energy expenditure
Example:
– activity factor for moderately active men = 45 65% of BMR (REE)
– BMR (REE) from previous example = 1,764
– therefore total energy expenditure is
1,764 x 0.55 + 1,764 = 2734 kcal
energy of physical activity
BMR (REE)
Table 804, page 250
Physical Inactivity
• favours a positive energy balance
• changes in lifestyle over the last century
– sedentary work
– sedentary recreation
Thermic Effect of Food (TEF)
• an estimation of the energy required to
process food
• includes energy needed to digest, absorb,
transport, metabolize, and store food
• proportional to the food energy consumed
• estimated as: 5 - 10% of energy intake
• influenced by meal size, frequency and
composition
Adaptive Thermogenesis
• energy expended when an individual
must adapt to change (e.g. stress,
extreme cold, starvation, trauma)
• extremely variable and highly specific
• NOT included when calculating energy
requirements
What determines a healthy
weight?
Social perceptions?
Health Risks?
Hypertensio
n
Diabetes
Arthritis
CVD
Body Mass Index (BMI)
weight (kg)
BMI 
2
[height (m)]
< 18.5
18.5 - 24.9
25 - 29.9
> 30
underweight
normal
overweight
obese
Weakness of BMI?
• does not account for body
composition or body fat
distribution
• proportion of body weight that
is FAT is more important for
determining health risk
Kevin Bieksa, BMI = 27.8
Body Composition
• measurement of % body fat
• techniques to measure include:
– densitometry
• underwater weighing
• air displacement
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DEXA
isotope dilution
skin fold thickness
bioelectrical impedance
CT scanning or MRI
near infrared interactance
Body Composition
Essential Fat
• crucial for normal body
functioning
Non-essential Fat
• most accumulates in
VISCERAL adipose
tissue
Body Fat Distribution
Android (Central Obesity)
• apple shape
• more common in men
and post-menopausal
women
• associated with increased
health risks
Body Fat Distribution
Gynoid (Lower Body
Obesity)
• pear shape
• more common in premenopausal women
• pattern encouraged by
estrogen &
progesterone
Waist Circumference
• reliable predictor of fat distribution
and abdominal fat
• measured around abdomen, just
above crest of the hip
Health Risks of Overweight
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cardiovascular disease (CVD)
hypertension
Type II Diabetes
pulmonary disorders
sleep disorders (e.g. SLEEP APNEA)
gout
hypertension
various cancers
osteoarthritis
early mortality
Health Risks of Underweight
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nutrient deficiencies
reproductive problems
cardiac arrhythmias
immunodeficiencies
rough, dry, scaly skin
poor temperature regulation
osteoporosis and increased risk of bone
fractures
• early mortality
Not the whole story…
• body weight is only one risk factor of many for
chronic disease
• for example, also need to consider
cardiorespiratory fitness
– normal weight unfit men have more than 2x
risk of all-cause mortality than normal
weight physically fit men
– overweight fit men have LOWER
mortality risk than normal-weight unfit
men
Obesity
• the second leading cause of preventable
death after tobacco use
• defined as an excessively high amount of
body fat in relation to lean body mass
– BMI > 30
– percent body fat > 25% (men) or > 32%
(women)
– waist circumference > 40” (men) or > 35”
(women)
Causes of Obesity
Why do people consume more energy than
they expend?
Explanations are many…
– genetic/physiological
– environment
• physical
• cultural
• socioeconomic
• psychological
Genetics
Epidemiological Evidence
• identical twins are 2x as likely to weigh
the same compared to fraternal twins
• if both parents are overweight a child is
2x as likely to be overweight compared
to a child with only one overweight
parent
Physiology of Weight Gain
• an excess energy consumption beyond the
needs of the body results in energy being
stored
• the amount of fat in a person’s body reflects:
– the NUMBER of fat cells
– the SIZE of fat cells
• definitions: hyperplastic and hypertrophic
obesity
Fat Cell Development
• number of fat cells increases most during late
childhood and early puberty
• fat cell size increases as cells fill with lipids
• after a fat cell reaches its maximum size, it
may divide again
• with fat loss, the SIZE of the cells decreases,
but not the NUMBER
Increase in fat cell size if
energy intake exceeds
energy expenditure
Increase in fat
cell number
during growth
With fat loss, the size of
the fat cells shrinks, but
not the number
Increase in fat cell number
when fat cells reach their
maximum size
Lipoprotein Lipase (LPL)
• enzyme on adipose and muscle cells that
captures triglycerides from blood and
promotes storage of fat
• since obese individuals have more fat cells,
they have higher levels of LPL than lean
individuals
What does this mean for an obese individual
who may only have a modest excess of
energy intake?
Lipoprotein Lipase (LPL)
• activity of LPL is regulated by estrogen in
women and testosterone in men
Site of greatest LPL activity
Women
breasts, hips, thighs
Effect on Body Fat
Distribution
gynecoid shape
Men
abdomen
android shape
• lower body is less active in releasing fat from
storage
• weight loss increases LPL activity
Leptin
• peptide hormone coded for by the Ob gene
expressed in adipose cells
• stimulates hypothalamus to produce
melanocortins that inhibit appetite and
promote energy expenditure thus promoting
weight loss
• low levels result in increased production of
Neuropeptide Y by the hypothalamus
promoting weight gain
• levels increase with increased body fat; levels
decrease with loss of body fat
Leptin
• RARE genetic deficiency of leptin leads to
obesity
• leptin concentrations increase with weight
gain
• most obese individuals have high leptin levels
• suggests that obesity is associated with leptin
resistance
• leptin also has many other functions
Neuropeptide Y
The actions of neuropeptide Y include:
– causes CARBOHYDRATE CRAVINGS
– initiates eating
– DECREASES ENERGY EXPENDITURE
– INCREASES FAT STORAGE
These each favour a positive energy balance
and promote weight gain.
Ghrelin
• peptide hormone
secreted by the
stomach
• acts on the
hypothalamus to
increase appetite
by stimulating
release of NPY
Fad Diets
Tell-tale Signs of a Fad Diet
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promise dramatic weight loss
promote diets that are nutritionally unbalanced
promote extremely low energy intakes
dependant on food products and services
do not encourage permanent, realistic, lifestyle
changes
cost $$$$$
fail to inform clients about risks
promote unproven weight loss aids and miracle foods
rely on testimonials as evidence diet works
don’t include exercise
have lists of “good” and “bad” foods
Why diets don’t work…
The body DEFENDS itself against weight
loss!
Weight loss causes:
• increased LPL activity
• decreased thyroid hormone production
• decreased leptin
Why diets don’t work…
Other Factors…
• weight cycling
• preoccupation with food, may lead to binge
eating
• often associated with irritability, depression,
fatigue, poor concentration
• does not resolve other issues such as low
self-esteem, depression
• may lead to social withdrawal
• do not promote permanent healthy changes
to lifestyle
• unattainable weight loss goals can lead to
frustration and failure
Weight Cycling
• repeated dieting which produces rapid
weight loss is often unsuccessful
Subsequent diet
results in SLOWER
weight loss
Weight
Regain
Diet
Regain
Weight Gain
Time
Low Carb Diets
Examples:
• Dr. Atkin’s New Diet Revolution,
Carbohydrate Addicts, others…
Premise
• consume less than 20 – 50 g of carbohydrate
per day
• no limit on fat or protein intake
• promise rapid weight loss
• appealing because allowed to eat high fat
tasty foods
Low Carb Diets
Successful in promoting weight loss through
three primary mechanisms:
• low carbohydrate intake depletes glycogen
stores leading to an initial rapid weight loss
from water
• low carbohydrate leads to production of
ketones; the state of ketosis inhibits appetite
and decreases energy intake
• diets tend to be low in total energy intake and
all diets that reduce caloric intake result in
weight loss
Low Carb Diets: Health Risks
• nutritionally inadequate
– risk deficiencies of Vitamin E, A, folate, calcium,
dietary fiber and others
• high in total and saturated fat
– increases risk of CVD
• causes ketosis and associated metabolic
risks
• dehydration
– increased urine production to excrete by-products
of protein metabolism
• increased risk of kidney disease
Treatment of Obesity
• only 5% of individuals who successfully lose
weight maintain their losses for at least a
year
Healthy Weight Loss Goals and Strategies
• make SMALL changes
• set REALISTIC expectations (for amount of
weight loss within a reasonable time frame)
Effective Weight Loss
Weight loss is most effective if it:
• is achieved GRADUALLY over time
• embraces HEALTHY eating
• incorporates PHYSICAL ACTIVITY
A reasonable weight loss rate for overweight
individuals is:
– 0.5 – 2 lbs per week
– 10% of body weight over six months
Establish REALISTIC Goals
• what are goals based on?
– societal standards or physical attractiveness?
– improved health and reduced risk of chronic
disease?
• a modest weight loss can still have health
benefits even if an individual remains
overweight
• unattainable weight loss goals can lead to
frustration and failure
Develop a Healthy Eating Plan
• severe energy restriction can have serious
detrimental consequences
• a minimum of 1200 kcal per day is required to
maintain nutritional adequacy
• reasonable suggestion: 500 kcal deficit per
day
– equivalent to about 1 pound per week (1 lb
body fat = 3500 kcal)
– achieve through combination of decreased
energy intake and increased physical
activity
Tips for Eating Plans
• eat small portions and eat slowly
– satiety signal indicating fullness is sent after a 20
minute lag
• focus on complex carbohydrates
– such as fresh fruits, vegetables, legumes, and
whole grains
– high fiber foods contribute more to satiation and
satiety
• limit high fat foods
– high fat meals lower blood leptin levels
Tips for Eating Plans
• limit empty calorie foods
– includes high sugar and alcohol as well as
fat
• drink adequate water
– need to meet water needs that were
formerly provided by eating extra food
– fills stomach between meals
Incorporate Physical Activity
• individuals who combine BOTH diet and
exercise in a weight loss program are
more likely to:
– reduce body fat
– retain more lean muscle mass
– regain less weight
Incorporate Physical Activity
• Regular activity has many benefits
• 200 kcal expenditure
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walking for 1 hour
cycling for 30 min
swimming for 20 min
running for 15 min
• Lifestyle change - activity habits and daily
routine
– quick walks, stairs, fidgeting
Weight-Related Benefits of
Exercise
• short term increase in energy expenditure
• long term increase in energy expenditure due
to increased in lean tissue which increases
BMR
• improves body composition
• helps with appetite control
• decreases stress
• improves self-esteem & psychological wellbeing
Behaviour Modification
Strategies
• identify problem eating behaviours and
develop alternate activities
e.g. replace snacking while watching TV with going
for a walk, stretching exercises, etc…
• change the environment to reduce stimuli that
encourage eating
e.g. keep fridge stocked with fruits and vegetables
instead of cookies, chips and crackers
• identify the reason why you eat
e.g. if stress, use exercise to relieve instead
Behaviour Modification
Strategies
• monitor your habits
e.g. what foods you eat, when ,where, and
why you eat
• develop supportive relationships with
others or attend a support group
• adopt permanent lifestyle changes to
achieve and maintain a healthy weight
Weight Maintenance
• expect a plateau within about 6 months
• important to continue with healthy lifestyle
changes, including exercise
• formerly overweight and obese individuals
need less energy to support needs than
individuals who have never been overweight
due to:
– increased efficiency at storing fat
– lower BMR associated with weight loss
Weight Maintenance
Characteristics of Weight Loss Maintainers
• lose weight slowly with small changes in
eating and physical activity
• consume regular meals
• exercise regularly
• make conscious efforts to avoid weight gain
• change habits without depriving themselves
of foods they enjoy
• depend on social support
• confront problems directly
Weight Maintenance
Characteristics of Weight Regainers
• do not employ behaviour modification
strategies
• change diet radically to lose weight
• do not include exercise as part of weight loss
program
• eat unconsciously in response to stress
• take diet pills
• lack social support
• avoid problems rather than face them directly
Aggressive Obesity Treatment:
Drugs
There is NO effective drug to treat obesity
that can be used over time without
adverse side effect or the potential for
abuse!
Sibutramine (Meridia)
• inhibits uptake of neurochemical in the brain
called serotonin
• results in reduced appetite
Aggressive Obesity Treatment:
Drugs
Orlistat (Xenical)
• inhibits activity of pancreatic lipase to block
fat digestion and absorption by 30%
• taken with meals, most effective when
combined with a reduced energy and low fat
diet
Benzocaine
• anesthetizes the tongue & decreases taste
• marketed under trade names of Slim Mints
and Diet Ayds
Surgery
• limit food intake
by reducing the
size of the
stomach