Healthy human diet
Home learning focus
A balanced diet contains the different nutrients in the correct amounts to keep us healthy. Learn what makes a healthy human diet.
This lesson includes:
- two videos to help you understand about nutrients and a healthy human diet
- two practise activities to help reinforce learning
To keep healthy, it is vital to eat a balanced diet. This means eating foods that contain nutrients in the correct amount.
In this film from learn about a healthy diet from a catering supervisor.
A nutrient is a substance needed by organisms to stay alive and healthy. A healthy human diet involves a number of different kinds of nutrients:
- lipids(fats and oils)
Dietary fibre cannot be absorbed by the body and contains no calories or vitamins, so is not a nutrient. However, it is really important in a healthy diet as it provides roughage to help keep food moving through the digestive system.
Some foods are particularly rich in certain nutrients. The table shows why we need each nutrient, and some good sources of each one:
|Nutrient||Use in the body||Good sources|
|Carbohydrate||To provide energy||Cereals, bread, pasta, rice and potatoes|
|Protein||For growth and repair||Fish, meat, eggs, beans, pulses and dairy products|
|Lipids (fats and oils)||To provide energy. Also to store energy in the body and insulate it against the cold.||Butter, oil and nuts|
|Minerals||Needed in small amounts to maintain health||Salt, milk (for calcium) and liver (for iron)|
|Vitamins||Needed in small amounts to maintain health||Fruit, vegetables, dairy foods|
|Water||Needed for cells and body fluids||Water, fruit juice, milk|
It is important to eat nutrients in the correct amounts – too much of certain nutrients may cause obesity and too little can cause malnutrition.
The World Health Organisation recommends getting at least half of your energy intake from carbohydrates and no more than 30% from fats. The organisation also recommends 400 g of fruit and vegetables daily.
'Obese' is a medical term used to describe a person with a high excess of body fat. A person is obese if their body mass index (BMI) is greater than 30 kg/m².
In this film learn about obesity from a school fitness adviser.
How does a person become obese?
A person becomes obese by eating food that supplies more energy than they need.
A 13-year old girl needs about 9,000 kilojoules (KJ) of energy each day. Boys the same age needs around 10,000 KJ/day. Adult women need roughly 8,400 KJ/day and adult men need roughly 10,500 KJ/day. If people consistently eat food that supplies more energy than this, without taking extra exercise, they are likely to become obese eventually.
A person can prevent obesity by eating sensible amounts of nutritious food and exercising regularly. Most obese people can lose weight by eating less and exercising more.
Health problems related to obesity
Obesity increases the risk of life-threatening health problems, including:
- Heart disease
- Type-2 diabetes
- Some types of cancer, including cancers of the breast, bowel and liver
Malnutrition happens when people do not eat the right amounts of nutrients. Malnutrition can occur all over the world - it is not just a problem in developing countries.
Eating too little food can cause two types of malnutrition:
- Acute malnutrition - when a person is at immediate risk of dying
- Chronic malnutrition - when a person does not grow or develop fully
Malnutrition can also occur when people eat too much food or large amounts of foods that are high in fat or sugar.
These people may become overweight or even obese. Obesity can lead to life-threatening conditions, including type-2 diabetes, heart disease and some types of cancer.
Some people eat enough food to supply their energy needs, but are short of certain vitamins and minerals. This causes deficiency diseases. For example:
- Iron deficiency causes anaemia. This leads to tiredness and shortness of breath
- Vitamin A deficiency can result in blindness
- Vitamin C deficiency causes scurvy, with bleeding gums, bulging eyes and scaly skin
- Protein deficiency can affect many body functions, often resulting in swollen, puffy skin and muscle wastage
There are lots of fun ways to practise what you know about a healthy human diet.
Healthy diet quiz
Try this quiz to test how much you know about a healthy human diet:
There's more to learn
Have a look at these other resources around the BBC and the web.