Energy balance, glycaemic index and fuel use

Overview

Energy balance and daily energy needs, worked meal energy figures, the glycaemic index and its values, low-GI foods before a marathon, rebound hypoglycaemia, fuel use by intensity and duration, and the respiratory exchange ratio.

What you need to know

Answer each one before you reveal it.

Questions from this subtopic

Each one with the model answer underneath.

1. 1

   What is energy balance, and what happens when it is positive or negative?

   Model answer

   Energy balance is when energy intake equals energy expenditure, so body mass stays stable. A positive balance leads to weight gain and a negative balance to weight loss.

2. 2

   In what units is the energy in food measured?

   Model answer

   Food energy is measured in kilojoules (kJ) or kilocalories (kcal). A kilocalorie equals about 4.2 kilojoules.

3. 3

   How much energy does an average adult need each day?

   Model answer

   The NHS guide is about 2,000 kcal a day for an average woman and 2,500 kcal for an average man. Active performers need considerably more.

4. 4

   A meal contains 80 g of carbohydrate, 20 g of fat and 30 g of protein. What is its energy content?

   Model answer

   The meal provides 620 kcal. The working is 320 + 180 + 120 = 620 kcal, using 4, 9 and 4 kcal per gram.

5. 5

   A 620 kcal meal contains 20 g of fat. What percentage of its energy comes from fat?

   Model answer

   Fat provides about 29% of the meal's energy. The working is 20 g × 9 kcal = 180 kcal, and 180 ÷ 620 × 100 = 29%.

6. 6

   What is the glycaemic index?

   Model answer

   The glycaemic index ranks carbohydrate foods by how quickly they raise blood glucose. Pure glucose is the reference, with a value of 100.

Other ways to work this

The same content, four other ways.

What is inside Levo

Six ways to work the same material.