Diet, hydration and energy use

Overview

Energy from each nutrient with worked calculations, energy balance, carbohydrate loading, meal timing, dehydration and its effects, and staying hydrated in sport.

What you need to know

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Questions from this subtopic

Each one with the model answer underneath.

1. 1

   How much energy does one gram of carbohydrate, protein and fat provide?

   Model answer

   Carbohydrate and protein each provide about 4 kcal per gram. Fat provides about 9 kcal per gram, more than twice as much.

2. 2

   A pre-match snack contains 45 g of carbohydrate. About how much energy does the carbohydrate provide?

   Model answer

   The carbohydrate provides about 180 kcal. The calculation is 45 g × 4 kcal per gram = 180 kcal.

3. 3

   What is meant by energy balance?

   Model answer

   Energy balance is when the energy taken in from food equals the energy the body uses. Body weight then stays roughly the same.

4. 4

   What happens to body weight when energy intake is greater than energy expenditure?

   Model answer

   When intake is greater than expenditure, the extra energy is stored as fat, so body weight increases. Body weight falls when expenditure is greater than intake.

5. 5

   A triathlete uses 3,600 kcal on a training day but eats only 3,100 kcal. What is the energy balance, and what happens if this continues?

   Model answer

   The triathlete has an energy deficit of 500 kcal a day. Body weight will fall if the deficit continues.

6. 6

   What factors affect how much energy a person needs each day?

   Model answer

   Daily energy needs depend on age, sex, body size and how active the person is. A very active performer needs far more energy than a sedentary person.

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