Transcript Nutritional Factors

Nutritional Factors
Influencing Body Composition
Overconsumption
• The government recommends 1600 calories a
day for the average sedentary woman and 2200
for men.
• In 2000, our reported per capita daily caloric
consumption was 1877 for women and 2618 for
men.
Nutrition and Exercise
Where do we get the energy for movement?
What should we eat to insure optimal health
and fitness?
Nutrition and Exercise
• Energy for movement comes from the food we
eat.
• The three sources of energy are:
– Carbohydrates
– Fats
– Proteins
Nutrition and Exercise
General Recommendations:
• CHO 55-65%
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CNS
Primary fuel source
Only anaerobic fuel source
Required for fat metabolism
Required for protein metabolism
Nutrition and Exercise
• Fat
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20-30%
Major fuel source for endurance activity
Essential component of cell membranes and
nerve fibers
Insulation
Shock absorption
Hormone production
Fat soluble vitamins
Nutrition and Exercise
• Fat
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High in kcal per weight
Low fat = <20%
Read labels - for something to be low fat, there
should be no more than 1 gram of fat for every 50
kcals.
100 kcals : 2 g fat = 18% fat (9 kcals per gram of fat)
Nutrition and Exercise
• Protein
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10-15%
Growth and maintenance of lean tissue
Repair of damaged tissue
Fuel source during starvation
Old Food Guide Pyramid
Food Guide Pyramid
• Key Points (2004):
– At least 3 one-ounce servings of whole grains each day
(instead of refined sugars and white bread)
– Whole grains contain more fiber which has been shown to
reduce the risk of heart disease and diabetes
– Increase daily intake of fruits and vegetables, whole grains,
and nonfat or low fat milk and milk products
Food Guide Pyramid
www.mypyramid.gov
Nutrients
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CHO
Fat
Protein
Water
Vitamins
Minerals
Vitamins
• Fat Soluble
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ADEK
• Water Soluble
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B Complex
C
Free Radicals and Antioxidants
• Free-radical generation increases after acute
exercise and potentially causes oxidative tissue
damage.
• May lead to cancer.
• Consuming antioxidants (e.g., vitamin E and βcarotene) can trap free radicals and prevent this
action.
Minerals
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Calcium
Phosphorus
Magnesium
Iron
Potassium
Sodium
Calcium
• RDA for most adults = 1000 mg
– For teenagers = 1300 mg
– For those over 50 = 1200 mg
– Highest food sources are dairy and calciumfortified orange juice.
Iron
• RDA = 8 mg for men and postmenopausal
women
• 18 mg for pre-menopausal women
• 27 mg for pregnant women
– Upper limit = 45 mg or stomach upset can
occur.
Zinc
• RDA = 11 mg for men, 8 for women
• Upper limit = 40 mg
• More can block absorption of another vital
nutrient, copper.
Water
• Important before, during, and after physical
activity.
• 2.5 liters per day.
• Major factor limiting exercise performance.
• Thirst.
Dieting
• Starvation diets will cause weight loss.
• However, they also cause physiologic
dysfunction and potentially death.
• In addition to fat loss, you lose muscle mass,
bone mass, and water volume.
Yo-Yo Dieting
• The more you diet, the fatter you become.
• When you lose, you lose muscle, fat, water, and
bone.
• When you return to your normal lifestyle, you
add on fat and water, but unless you increase
activity levels drastically, you don’t add bone or
muscle mass.
Fad Diets
• Why are they so popular?
• They give the false impression that you can eat
what you like, in the quantities that you want,
without having to exercise, and still lose weight.
• Very seductive message.
Low Carb
• Hype:
– Carbs are not healthy
– Carbs negatively impact blood sugar levels through
high glycemic index raising insulin levels
– Low blood sugar leads to hunger
– Invented concept of “Net Carbs”
Low Carb
• Facts:
– Low blood sugar hasn't been directly linked to
hunger.
– Unless you have diabetes, blood sugar remains
generally stable anyway.
– When you stop eating carbohydrates, your brain
stops regulating serotonin, a chemical that elevates
mood and suppresses appetite.
Low Carb
• Facts:
– Only carbohydrate consumption naturally stimulates
production of serotonin.
– When serotonin is made and becomes active in your
brain, its effect on your appetite is to make you feel
full before your stomach is stuffed and stretched.
– The brain makes serotonin only after a person
consumes sweet or starchy carbohydrates.
Low Carb
• Facts:
– The kicker is that these carbohydrates must be eaten
in combination with very little or no protein.
– This can explain why people may still feel hungry
even after they have eaten a 20-ounce steak.
– Their stomachs are full but their brains may not be
making enough serotonin to shut off their appetites.
Low Carb
• August 1st, 2005 Atkins Nutritionals declares
bankruptcy
Body Composition Questions
• Why do low-carbohydrate diets produce such a
rapid weight loss?
• Diets that limit or totally exclude CHO produce
a rapid weight loss.
• When CHO intake is low, muscle glycogen
stores are depleted rapidly.
Body Composition Questions
• For every gram of CHO, 3 grams of H20 are
stored in the body.
• When glycogen stores are depleted, the loss of
water leads to a dramatic weight loss because
each liter of water weighs approximately 2 lbs.
Body Composition Questions
• The weight is regained rapidly, however, when
CHO intake returns to normal.
Protein Power
• 850-1,100 kcal/d
• High protein
The Zone
• 1,300 kcal/d for women and 1,700 kcal/d for
men
• Follow the 40-30-30 rule
• No foods are off limits, but they claim some
foods are better than others
– Example – broccoli, celery, and grapes = good
– Cereal, bagels, and bananas = bad
• No real justification for these classifications
Sugar Busters!
• 1,200 kcal/d with 28% of total energy intake
from fat
• 33% of total energy intake from protein
South Beach Diet
• Steer clear of bread and beer (maltose)
• No fruit, bread, sugary snacks, potatoes, pasta,
or rice
• No scientific support for these
recommendations, but at least allows whole
grains, some fruit (later), and cuts back on
saturated fat
Nutrition Questions
• Why are low carbohydrate diets unsafe?
• Low CHO intake may lead to fatigue,
hypoglycemia, and ketosis.
Nutrition Questions
• Low carb diets are detrimental to anaerobic
work capacity because of reduced muscle
glycogen stores and decreased rate of glycolysis.
Nutrition Questions
• Many of the fad diets (Atkins Diet Revolution,
Sugar busters, the Zone) result in weight
reduction primarily because they are low calorie
diets.
Nutrition Questions
• Low carb diets are high in fat, saturated fat, and
cholesterol.
Nutrition Questions
• The nature of low carb diets is a diet low in
fruits, vegetables, grains, and beans.
• These foods are all high in health promoting and
disease preventing properties.
Nutrition and Exercise
• Do we need to consume large amounts of
protein if we exercise and wish to increase
muscle mass?
Nutrition and Exercise
Recommended Levels of Protein Consumption
RDA
Sedentary Endurance
Strength
g/kg/day
0.8
1.2 - 1.4
1.4 - 2.0
Nutrition and Exercise
• “No valid evidence exists supporting the notion
that protein intake exceeding 1.8 - 2.0 will
provide additional advantage”
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International Journal of Sports Nutrition
Nutrition and Exercise
• “The recommended levels may be reached
within the total protein percentage
recommendations of 10-15% of all calories
consumed daily”
• International Journal of Sports Nutrition
Nutrition and Exercise
• Example
220 lbs male = 100 kg
– excessive intake = 2.0 (g/kg/day)
– daily need = 200 grams
– typical consumption = 6000 kcals
10-15% of 6000 kcal = 600 -900 kcal of protein
– divided by 4 kcals per gram
– 150-250 grams of protein.
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Amino Acids and Protein
• In all but a few exceptional cases, the maximal
contribution of protein as an energy source
during exercise ranges between 2% and 10% of
the total energy expended.
– (Gibala; Hargreaves, and Tipton, 2000)
Amino Acids and Protein
• In theory, amino acids could contribute to
carbohydrate metabolism during exercise, but
there is no hard evidence that this occurs or has
any bearing on sport performance.
– (Gibala; Hargreaves, and Tipton, 2000)
Amino Acids and Protein
• Supplementation of the athlete’s diet with
branched-chain amino acids apparently does not
benefit exercise performance.
– (Gibala; Hargreaves, and Tipton, 2000)
Amino Acids and Protein
• The most important factors for optimizing
growth when one performs resistance exercise
are:
• Adequate resistance
• Adequate caloric consumption, including just
after lifting
• Plenty of rest between sessions
– (Gibala; Hargreaves, and Tipton, 2000)
Amino Acids and Protein
• With rare exceptions athletes require 1.2 – 1.6
grams of protein per kg day.
• This amount of protein can almost always be
obtained in the normal diet.
– (Gibala; Hargreaves, and Tipton, 2000)
Amino Acids and Protein
• There is no solid evidence that special mixtures
of amino acids provide any advantage over
normal dietary proteins in stimulating muscle
growth.
– (Gibala; Hargreaves, and Tipton, 2000)
Nutrition Questions
• Are high-protein diets safe?
• High-protein diets that limit CHO intake
promote muscle tissue loss.
• When CHO intake is restricted, the glucose
needs of the body are met by breaking down
proteins.
Nutrition Questions
• Excessive protein intake does not promote
protein synthesis.
• Instead the excess protein is metabolized.
Nutrition Questions
• The amino acids are deaminated, the excess
nitrogen is excreted in the urine as urea, and the
remaining carbon skeleton is converted to
glucose or used as an energy fuel.
Nutrition Questions
• Some high-protein diets require drinking large
quantities of water to prevent the dehydration
caused by excess urea production and to wash
away ketone bodies.
Nutrition Questions
• Dehydration and the additional stress placed on
the kidneys may be potentially dangerous,
especially for individuals with kidney problems
or gout.
Nutrition Questions
• Protein intake above 2.8 g/kg/d has been
shown to impair renal function.
• High-protein diets may promote urinary calcium
loss which is particularly a concern for women
bodybuilders.
Nutrition Questions
• Are high-fat diets unsafe?
• Yes
• They produce high levels of serum cholesterol
and triglycerides which may lead to
atherosclerosis.
Nutrition Questions
• Typically high-fat diets are high in calories,
therefore a smaller volume of food must be
consumed.
• There are no metabolic pathways in the body for
converting fatty acids to glucose, so excess fat is
stored in adipose tissue.
Nutrition Questions
• What is the danger of fasting or skipping meals
to promote weight loss?
• Potential side effects include kidney
malfunction, hyperuricemia, loss of hair,
dizziness, fainting, and muscle cramping.
Nutrition Questions
• When the body is deprived of food, it responds
by increasing the fat-depositing enzymes and
storing more fat.
• The body will also metabolize protein to meet
its energy needs.
• Body will absorb more of the food that appears
in digestive system.
Nutrition Questions
• Why should a fat loss diet include at least 5565% carbohydrates?
• CHO helps maintain normal function of the
nervous system because nerve tissue relies solely
on glucose as a fuel for energy.
Nutrition Questions
• Consuming adequate amounts of CHO on a
daily basis prevents the depletion of glycogen
stores and the need to synthesize glucose from
the body’s protein (protein-sparing effect).
Nutrition Questions
• When glycogen stores are depleted, the glucose
needs of the body are met through the
breakdown of muscle protein.
• This leads to a loss of lean tissue rather than fat.
Nutrition Questions
• CHO is also essential for fat metabolism.
• When CHOs are restricted or CHO stores are
depleted, more fatty acids are mobilized from
adipose tissue that can be metabolized by the
body.
Nutrition Questions
• This results in the incomplete breakdown of
lipids and the formation of ketone bodies that
may cause ketosis.
Nutrition Questions
• In addition, muscle glycogen and glucose are the
primary fuels used during intense, short-term
exercise and prolonged, submaximal exercise.
Nutrition Questions
• Inclusion of adequate amounts of CHO in the
diet prevents depletion of muscle glycogen and
the consequent reduction in endurance
performance.
Sugared Drinks
• High levels of intake of sugar-sweetened drinks
and of fruit juice raise weight over time in
educated women in their 30s (Schulze, 2004)
• Higher intake of diet soft drinks reduces weight
gain
Sugared Drinks
• Higher take of sugar-sweetened drinks raise the
risk for type 2 diabetes in women without a
family history of diabetes.
• Does not appear true for fruit juice
Sugared Drinks
• Low levels of sugar-sweetened drink intake does
not increases weight gain or diabetes over time.
Athletes and Nutrition
• Swimmer Michael Phelps’s next career may be in competitive
eating.
• Besides grabbing five gold medals at the Beijing Olympics so far,
making him the winningest Olympic athlete ever, he’s got to be
setting new marks on the chow line.
• A New York Post account of Phelps’s… wait for it… 12,000calorie-a-day diet, gave us a stomachache.
Athletes and Nutrition
• Could one human being really consume that
much and still be in Phelps’s shape?
• And could this possibly be healthy for Phelps,
even considering his five-hours-a-day, six-daysa-week exercise regimen?
Athletes and Nutrition
• Here’s Phelps’s typical menu.
• No, he doesn’t choose among these options.
• He eats them all, according to the Post.
• Breakfast: Three fried-egg sandwiches loaded with cheese,
lettuce, tomatoes, fried onions and mayonnaise. Two cups of
coffee. One five-egg omelet. One bowl of grits. Three slices of
French toast topped with powdered sugar. Three chocolate-chip
pancakes.
Athletes and Nutrition
• Lunch: One pound of enriched pasta. Two
large ham and cheese sandwiches with mayo on
white bread. Energy drinks packing 1,000
calories.
• Dinner: One pound of pasta. An entire pizza.
More energy drinks.
Athletes and Nutrition
• Does a diet like this make sense even for a calorie-incinerating
human swimming machine?
• If you eat fewer calories than you burn exercising, you lose
weight.
Athletes and Nutrition
• But an athlete like Phelps, who exercises up a
storm, has to worry about eating enough to
replenish the scads of calories he’s burned.
• If he doesn’t, his “body won’t recover, the
muscles will not recover, there will not be
adequate energy stored for him to compete in
his next event.”
Athletes and Nutrition
• But what about the choice of foods?
• All those eggs and ham and cheese can’t possibly be good for
him, can they?
Athletes and Nutrition
• Says Klion, “I think for him, because of his caloric demands, he
can probably eat whatever he wants to.”
• And besides, Klion says, if you’ve got to eat that much, it better
be enjoyable, or you won’t be able to keep up.
• Phelps might not be so eager to shovel down a pound of tofu in
a sitting, Klion points out.
Athletes and Nutrition
• Still, Klion cautions that he knows plenty of athletes who’ve
been training for marathons and have gained weight because
they thought they could eat whatever they wanted.
• So it really does take some planning.
Athletes and Nutrition
• Normal standards don’t really apply to a someone like Phelps,
who exercises way more vigorously than the typical person.
• Even by athletic standards, Phelps is in his own league.
• Cyclists in the Tour de France commonly consume a paltry 8,000
to 10,000 calories a day.