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Nutrition
Learning Objectives:
1. To be able to explain BMR, Body Fat
Percentage and Obesity.
2. To know the 7 classes of food and
their role in a healthy diet.
3. To understand the dietary needs of
various athletes.
Energy
• The amount of energy needed depends on activity
levels and basal metabolic rate (BMR).
• BMR is the rate at which a person uses energy. It
depends on gender, age and physique.
• Young people have high BMR due to their growth and
development.
• Men usually have a higher BMR due to greater muscle
mass.
• BMR accounts for about 75% of our energy needs.
Percentage Body Fat
• Ideally, energy intake should equal energy required.
• Any excess energy taken in will be stored as fat.
• On average men have 10-20% body fat and women
15-25%.
• Body fat % can be measured by: skinfold measures,
bioelectrical impedance or water submersion.
Obesity
• Obesity is a condition where a person’s percentage
body fat is over 40% or when their BMI is above 30.
• BMI (body mass index) is your height to weight ratio.
• A BMI above 40 is strongly linked to a range of diseases
including cancer, heart disease, diabetes and high
blood pressure.
• Causes include inactive lifestyles, inactive jobs, and
overeating.
Overcoming Obesity
• Overweight individuals often find it difficult to be
physically active.
• The Department of Health recommends at least 30
minutes of exercise 5 days a week.
• Only 37% of men and 25% of women do this.
• A lack of physical activity among children is an
increasing growing problem.
7 Classes of Food
Carbohydrates – provide the body with energy.
Fat – used as an energy source during rest and low
intensity exercise.
Protein – used for growth and repair and a minor energy
source.
Fibre – helps the digestive system.
Minerals – required for functions such as bone growth,
energy metabolism and nerve function.
Vitamins – complex substances with a variety of functions
including energy metabolism and tissue formation.
Water – essential for functioning of nearly all cells.
Carbohydrates
• Carbohydrates are converted to glucose to provide
energy.
• Excess glucose is stored as glycogen in the liver and
muscles (and then fat when stores are full).
• High levels of activity will use up the available
glucose, then stored glycogen and fat.
• Carbohydrates are found in potatoes, bread, rice
and pasta.
Fat
• Fat is made up from fatty acids and glycerol.
• Triglyceride is a simple fat found in adipose (fat) tissue
and muscle.
• Fat contains more than double the energy of
carbohydrates.
• Fat requires large amounts of oxygen to break it down
and so can only be used for low intensity exercise.
• Fat is also a carrier of fat-soluble vitamins.
• High fat intake (particularly saturated fat) has been
associated with raised blood cholesterol level and
heart disease.
Protein
• The building block of proteins are amino acids.
• Protein is needed for growth and repair.
• Athletes in strength and power-type activities will be
repairing and developing muscle tissue.
• Protein is found in meat, fish, eggs, milk, nuts.
Fibre
• Fibre acts as a bulking agent and prevents
constipation.
• It is often a part of the diet that is neglected.
• Fibre is found in whole-grain and high-fibre cereals.
Minerals
Minerals are required for a variety of functions and include:
• Calcium – formation of bones and teeth. Found in milk
and cheese.
• Magnesium – required for energy metabolism and
electrolyte balance. Found in grains and nuts.
• Sodium – helps regulate water content, electrolyte
balance and nerve function. Excess sweating causes
sodium depletion whilst too much salt in the diet is linked
to high blood pressure.
• Potassium – essential for water and electrolyte balance.
Found in fruit and vegetables.
• Iron – required for haemoglobin in red blood cells and to
aid the immune system. Found in broccoli and Guinness!
Vitamins
Complex substances needed in small amounts for many
functions. Fat soluble vitamins include:
• Vitamin A – essential for skin and mucous membranes,
as well as the immune system, vision and normal
growth. Found in liver, milk, cheese.
• Vitamin D – works as a hormone controlling the
amount of calcium absorbed by intestine as well as
bone structure. Found on oily fish, eggs, the sun.
• Vitamin K – essential for clotting blood. Found in meat
and veg but also made in the gut.
Vitamins (cont…)
Water soluble vitamins include:
• Vitamin C – involved in production of connective tissue
(skin, cartilage, bone) as well as the function of blood
vessels. Found in oranges.
• Vitamin B1 – needed for release of carbohydrate.
Found in whole grain, nuts, pork.
• Vitamin B2 – needed to release energy from protein,
carbs, fat. Found in milk, eggs, cereal.
(and several more; see textbook for details)
Water
• Over half the body consists of water and all living cells
depend on it.
• Provides the medium in which most reactions in body
occur.
• Acts as lubricant for joints and eyes.
• Helps to regulate body temperature.
• Amount required depends on age, climate, diet,
activity levels.
• Dehydration can cause impaired physiological
responses, lower performance level and fatigue.
• Water replacement is essential before, during, and
after exercise. Isotonic drinks can replenish water and
carb levels more quickly.
Balanced Diet
• A balanced diet is one which contains sufficient
amounts of the nutrients required by the individual.
• For most, eating a more balanced diet means:
eating more fruit and veg, eating more starchy
food (bread, potato, rice, pasta), eating leaner
meat and less fat.
Benefits of Physical
Activity
Physical activity has been shown to have numerous
benefits including:
• Reducing risk of cardiovascular disease, high blood
pressure, diabetes, obesity and cancer.
• Improves mental wellbeing, strengthens skeleton and
maintains a healthy weight.
• Promotes strength, coordination and balance.
Different Diet for Athletes
• Marathon runners need greater amounts of
carbohydrates in order to provide energy for
prolonged periods.
• They also require greater amounts of fat to save carb
stores and because endurance training leads to
greater fat metabolism.
• Any athlete will need greater levels of vitamins and
minerals due to an increased metabolism level.
• Power/strength performers will also need greater
protein intake because of the need for muscle repair
and growth.