Nutrient balance - (http://www.brianmac.co.uk/nutrit.htm)

Nutrient Balance
Carefully planned nutrition must provide an energy balance and a nutrient balance.

The nutrients are:

Proteins - essential to growth and repair of muscle and other body tissues
Fats - one source of energy and important in relation to fat soluble vitamins
Carbohydrates - our main source of energy
Minerals - those inorganic elements occurring in the body and which are critical to its normal functions
Vitamins - water and fat soluble vitamins play important roles in many chemical processes in the body
Water - essential to normal body function - as a vehicle for carrying other nutrients and because 60% of the human body is water
Roughage - the fibrous indigestible portion of our diet essential to health of the digestive system
What are the daily energy requirements?
Personal energy requirement = basic energy requirements + extra energy requirements

Basic energy requirements (BER) includes your basal metabolic rate (BMR) and general daily activities

For every Kg of body weight 1.3 Calories is required every hour. (An athlete weighing 50Kg would require 1.3 × 24hrs × 50Kg = 1560 Calories/day)
For a calculation of your BMR, see the calculator on the Resting Daily Energy Expenditure (RDEE) page
Extra energy requirements (EER)

For each hours training you require an additional 8.5 Calories for each Kg of body weight. (For a two hour training session our 50Kg athlete would require 8.5 × 2hrs × 50Kg = 850 Calories)
An athlete weighing 50Kg who trains for two hours would require an intake of approximately 2410 Calories (BER + EER = 1560 + 850)

Energy Fuel
Like fuel for a car, the energy we need has to be blended. The blend that we require is as follows:

57% Carbohydrates (sugar, sweets, bread, cakes)
30% Fats (dairy products, oil)
13% Protein (eggs, milk, meat, poultry, fish)
The energy yield per gram is as follows: Carbohydrate - 4 Calories, Fats - 9 Calories and Protein - 4 Calories.

What does a 50 kg athlete require in terms of carbohydrates, fats and protein?

Carbohydrates - 57% of 2410 = 1374 Calories - at 4 Calories/gram = 1374 ÷ 4 = 343 grams
Fats - 30% of 2410 = 723 Calories - at 9 Calories/gram = 723 ÷ 9 = 80 grams
Protein - 13% of 2410 = 313 Calories - at 4 Calories/gram = 313 ÷ 4 = 78 grams


http://www.brianmac.co.uk/nutrit.htm