Energy Balance Revisited

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Sports Nutrition
Energy Balance Revisited
Energy Intake Energy Expend Energy Stored
? Control of Food intake
? Is Energy balance everything?
? Actual weight loss studies
? Energy balance in Sports
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Galen (200 BC) Hunger is in the brain
Cannon (1912) When you feel hunger it is
because the stomach contracts
What is controlled ? body weight body
fat glycogen stores
And how is this controlled?
Obesity is a major failure of modern medicine
society.
- 50 of all US adults are overweight.
- 30 are obese - a BMI of gt30.
- In the USA 300,000 deaths per year are from
obesity related diseases.
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? In rats, presented with a more diluted diet
they eat more. With a more concentrated diet
they eat less.
? Energy intake is controlled by the calorific
value of food.
? taste texture also play a role.
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? The hypothalamus in the brain has been found to
be an important regulator of appetite food
intake.
In animal experiments
? When the lateral area of the hypothalamus was
damaged rats lost all appetite, became
indifferent to food and would starve to death.
? The lateral area of the hypothalamus is a
hunger centre that drives appetite and food
intake.
? The ventral area is a satiety centre that
senses glucose levels.
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When there is sufficient glucose the ventral area
provides negative feedback to the lateral area,
and eating does not occur.
? Mayer put forward a gluco-static theory. The
desire for food depends upon the regulation of
blood glucose.
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Cabanac (1970)
- Taste pleasure is also involved in maintaining
glucose homeostasis (a set point).
In obese subjects no change after 50 gm glucose.
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There is evidence that the levels of other
macronutrients (both within the plasma and
overall body stores) also influence food intake.
Lipostatic theory - lipid levels regulate food
intake.
Aminostatic theory - amino acid levels regulate
food intake.
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? Overall many factors regulate food intake
Short-term satiety signals - Plasma levels of
nutrients (i.e. glucose) -
Hormones - Stretch receptors in the
stomach (i.e. food bulk).
Sensory Information - Taste, smell
Long-term Energy balance - Energy stores (i.e.
leptin) - Energy expenditure
The brain integrates this information and
controls behaviour, with the hypothalamus central
to this process.
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Is weight gain/loss all about Energy balance?
Energy Intake Energy Expend Energy Stored
Energy balance is by far the most important
factor in energy storage therefore body weight.
But if it is all about energy balance then
The composition of the energy intake and
expend is irrelevant. ( ? )
1. Does it matter that all energy intake comes
from fat ?
2. Is exercising in the fat burning zone
irrelevant ?
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Composition of Energy Intake
Horton et al., 1995.
Overeating fat CHO
90 - 95 of excess fat is stored.
75 - 85 of excess CHO is stored.
Excess CHO intake causes ? CHO oxidation and
total EE.
Excess fat intake does not influence fat
oxidation or total EE.
TEF is higher with excess CHO intake.
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Energy Density
? Satiety is partly influenced by food bulk.
? Foods high in fat have a high energy
density a lot of energy in relation to their
bulk.
? High fat foods seem to provide lt satisfaction
in relation to energy content.
? Foods high in CHO often contain fibre,
which has no energetic value, but increases food
bulk.
? High CHO foods provide gt satisfaction in
relation to their energy content.
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Body weight is a measure of energy balance
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Energy expenditure weight loss
? Adipose tissue is 83 lipid. ? 1 kg of
adipose tissue is 0.83 kg of lipid.
_at_ 9 kcal /g 7,719 kcal Running 1 mile
100 kcal.
? 1 kg of fat 77 miles of running !
? To lose 10 kg in a year 770 miles or 15
miles per week, with no increase in energy intake.
? Changes in weight due to EE are long-term
? For short-term changes it is easier to control
EI than EE.
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van Dale et al. 1987.
12 obese women 6 diet only 6 diet
and exercise (4 hrs / wk _at_ 50 VO2 max) for 12
weeks.
Diet Diet Ex Body wt -12.2 kg -13.2
kg
Fat loss -9.4 kg -10.9 kg
BMR per kg FFM
-26.5 -18.3
? Dieting can cause large reductions in body
mass, despite significantly reducing BMR.
? During short-term dieting periods exercise only
causes a small additional weight loss.
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Diet, exercise and weight loss
van Dale et al. 1990.
12 week diet / diet exercise treatment
(body mass D, -12 kg DE, - 16.5 kg)
Then 44 months follow-up
D, then normal Regained 90 of lost weight, and
SMR was - 15.8 of baseline.
DE, then normal Regained 60 of lost weight,
and SMR was - 15.8 of baseline.
DE, Continued Exercise Regained only 23 of
lost weight, and SMR was -3.7 baseline.
? Exercise makes an important contribution to
long-term weight reduction, by increasing EE
maintaining BMR.
Sleeping metabolic rate per kg FFM.
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Upper Limits of Energy Expenditure
? 9,000 - 11,000 kcal/day
? 3.5 - 5.5 ? BMR
Equivalent to 2.5 kg of CHO per day.
? Practical Problems - Strenuous exercise
suppresses hunger feelings. -
Gastro-intestinal distress.
? Difficult to achieve energy balance
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Lower Levels of Energy Intake
? Constant low weight. Chronically low energy
intake to maintain low body weight.
? Jockeys, gymnasts, dancers.
? Competition weight. Drastic weight loss regimes
to achieve desired weight category.
? Boxing, rowing, wrestling, judo.
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Constant Low Weight
- Amenorrhea. - Loss of bone mineral density. -
Tendancy to become obsessive about diet / body
weight / body image.
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Making competition weight
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Achieving competition weight - Weight Cycling
Steen Brownell, 1990
Surveyed weight loss for competition in High
School College Wrestlers.
? 60 of HS wrestlers had lost over 5 kg at
least once.
? 69 of College wrestlers had lost 5-9 kg at
least 11 times.
Implications of weight cycling - Increased CV
disease risk and all cause mortality. -
Increased psychological distress anger, anxiety
etc.
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Recommended Reading
Williams, C and Devlin, J.T. (1992) Foods,
nutrition and sports performance. EFN Spon,
London. Chapter 1 McArdle, WD, Katch, FI and
Katch, VL (1996) Sports Exercise Nutrition.
Lippincott, Williams Wilkins, Baltimore, USA.
Chapter 13 p 431. Brownell, KD, Rodin, J
Wilmore (1992) Eating, body weight and
performance in athletes. Lea Febiger, Penn,
USA. Chapters 2 11 Garrow, JS James WPT
(1993) Human nutrition and dietetics. Churchill
Livingstone, Ediburgh. Chapter 9
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0 mths 12 mths 18
mths Men BM (kg) 73.0 70.4 71.2
BF 16.6 13.8 13.4
Women BM (kg) 59.0 58.3 58.1
BF 25.0 23.1 22.8
Found - a decrease in body weight and body
fat - a slight increase in food intake, but
change in the composition of food intake
CHO? and Fat?
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? The hypothalamus in the brain has been found to
be an important regulator of appetite food
intake. Particularly the lateral and ventral
areas of the hypothalamus.
In animal experiments
? When the lateral area of the hypothalamus was
damaged rats lost all appetite, became
indifferent to food and would starve to death.
? The lateral area of the hypothalamus is a
hunger centre that drives appetite and food
intake.
But in healthy animals how does the lateral area
of the hypothalamus sense the need to eat ?
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Energy intake and body weight
Cross-sectional study of females
Energy intake Relative Wt
(Kcal/day) Tennis players 2417 1.01 Sedentary
1480 1.14
? Regular recreational participants have 65
greater EI, but lower body mass.
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? Put gold-thioglucose in animal feed as a tracer.
- Gold-thioglucose was found to destroy the
ventral area of the hypothalamus, and caused
animals to eat continuously.
? The ventral area is a satiety centre that
senses glucose levels.
When there is sufficient glucose the ventral area
provides negative feedback to the lateral area,
and eating does not occur.
? Mayer put forward a gluco-static theory. The
desire for food depends upon the
regulation of blood glucose.
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