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Sport Nutrition Education No. I - The Concept of Energy

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Whether you are an elite athlete or just someone who enjoys sports, proper nutrition should not be overlooked. Having a good appetite doesn't guarantee your diet is nutritionally adequate. Both quantity and quality of the food you eat should be considered when it comes to eating well. Therefore, eating whatever is available is definitely not a good meal plan.

Food provides the energy you need in daily activities. For this reason, what you eat and how much you eat must meet the specific needs of your event and training. For example, a marathon runner needs to replenish with food and fluid throughout the race; whereas a sprinter would not need to take any kind of supplementation during an event which takes less than a minute.

Eating properly gives you the fuel you need during training and competition. It is also an important component to winning.

Talent, hardwork combined with the expert guidance from your coaches and the right diet pave the road to victory.

What is Energy?

When food breaks down in your body, energy is released. Energy is the fuel for your daily activities. The unit of measurement for energy is kilocalorie (kcal), more commonly known as calorie (cal), but kilocalorie is the term used by most professionals.

Energy content of the six nutrients

1. Carbohydrate 4 kcal/g
2. Protein 4 kcal/g
3. Fat 9 kcal/g
4. Vitamin (eg. Vitamin A,B,C etc) no energy value
5. Mineral (eg. Calcium, Iron,Sodium, Potassium etc) no energy value
6. Water no energy value

Energy content of the two non-nutrients

1. Dietary Fibre no energy value
2. Alcohol 7 kcal/g

As you can see, fat has the highest energy density, more than twice of what's in carbohydrate.

Energy content in some foods

1 teaspoon sugar (pure carbohydrate) 16 kcal
1 boiled egg white (almost pure protein with trace amount of carbohydrate) 16 kcal
1 teaspoon corn oil (pure fat) 45 kcal
1 bowl of cooked rice 234 kcal
3 taels of lean meat 215 kcal
1 orange 50 kcal
1 cup skim milk 90 kcal

Energy Needs

To estimate your energy needs, the following factors need to be considered.

  1. Basal Metabolic Rate: The amount of energy needed to sustain necessary bodily functions (eg. pumping of the heart, breathing, blood circulation etc) when at rest. In simple terms, if your basal metabolic rate is 1200 kcal and you have slept the whole day without doing other activities, you would have burnt 1200 kcal on that day.

  2. Age: Your energy needs vary with age, for example :

    1. growing children and adolescents need more energy than adults.
    2. elderly needs less than adults
  3. Sex: Males need more than females of the same age.

  4. Health Condition: If you are sick, pregnant or lactating, your needs increase.

  5. Activity Level: Energy needs increase with increase activity level.

If your energy intake and output is not the same, you will experience weight change.

For example :

energy intake from food is more than energy output from activity -> weight gain
energy intake from food is less than energy output from activity -> weight loss
energy intake from food is about the same as energy output from activity

-> weight maintenance

Some athletes undergo long hours of training daily, therefore, they need a lot of energy.

For example, 
A male rower who trains for about 6 hours daily, he needs 5000 kcal/d to maintain his body weight. 
A family of three: Dad, Mom and 3-year old son;

  Dad needs 2200 kcal/d
  Mom needs 1700 kcal/d
  Son needs 1100 kcal/d
  Total for family 5000 kcal/d

If mom and dad exercise rarely, they would gain weight on their diets of 1700 kcal and 2200 kcal respectively.

For more information, please contact:
Sport Nutrition Unit
Telephone: (852) 2681 6277