A balanced diet is a diet in which all the components needed to maintain health are present in appropriate proportions.
The eatwell plate shows the proportions of the different components that should be eaten daily in a well-balanced diet.
A balanced diet should include appropriate proportions of carbohydrate, protein, lipid, vitamins, minerals, water and dietary fibre.
The amount of energy we need varies. This is due to the following factors:
The amount of energy we need tends to increase as we approach adulthood.
|Age in years||Daily energy requirement in kJ|
The energy needs of adults go down as they age. For example, people in their 50s need about 17 per cent less energy in their diet than people in their 30s.
People who are active tend to need more energy than sedentary people. For example, an adult office worker might need 10,000 kJ per day, but a manual worker might need 15,000 kJ per day.
In general, the greater a person’s mass, the more energy they need. Men tend to need more energy than women, and a woman’s energy needs increase when she is pregnant. This is mainly because she is carrying extra mass.
The energy content in a food sample can be measured using simple calorimetry.
To carry out this experiment, you need to:
To work out the energy per gram of food transferred to the water, use this equation.
Two crisp breads are tested to see which provides the most energy per gram.
0.7 g of crisp bread A is burned and increases the temperature of 10 cm3 of water by 15°C.
0.5 g of crisp bread B is burned and increases the temperature of 10 cm3 of water by 20°C.
Using the equation, calculate the energy transferred from each sample. If the answer is more than 1,000 joules, you should express the answer in kilojoules: 1,000 J = 1 kJ.
Note that 1 cm3 of water has a mass of 1 g.
Crisp bread A
Crisp bread B
Crisp bread B has the highest energy content.