Food, exercise and health

To stay healthy we need a balanced diet, regular exercise, good hygiene and enough sleep. A balanced diet has the right amounts of each food group, so we get all the nutrients we need: carbohydrates, proteins, fats, vitamins, minerals, fibre and water.

Key facts

  • Food groups: fruit and vegetables; starchy foods (bread, rice, pasta, potatoes); proteins (meat, fish, eggs, beans); dairy (milk, cheese, yoghurt); and small amounts of oils and spreads.
  • Carbohydrates and fats give us energy; proteins help us grow and repair the body; vitamins and minerals keep us healthy; fibre keeps food moving through the gut.
  • Too little of a nutrient causes a deficiency disease: scurvy (vitamin C), rickets (vitamin D or calcium), anaemia (iron).
  • Exercise makes the heart and muscles stronger. During exercise the heart beats faster to carry more oxygen to the muscles.
  • Washing your hands with soap and water for at least 20 seconds removes germs and stops them spreading.
  • Children need about 9 to 12 hours of sleep a night; teenagers need about 8 to 10.
  • The energy in food is measured in kilojoules (kJ). Energy we take in but don’t use is stored as fat.

Worked examples

Example 1

Which food group is each one in: an apple, a slice of bread, an egg, a glass of milk?

  1. An apple is a fruit: fruit and vegetables.
  2. Bread is made from wheat flour: starchy foods (carbohydrates).
  3. An egg is a protein food.
  4. Milk is dairy.

Answer: apple: fruit and vegetables; bread: starchy foods; egg: proteins; milk: dairy

Example 2

Thandi counts her pulse for 15 seconds: 24 beats at rest and 40 beats after running. What are her heart rates in beats per minute?

  1. There are 4 lots of 15 seconds in a minute. 60 ÷ 15 = 4
  2. At rest: 24 × 4 = 96
  3. After running: 40 × 4 = 160

Answer: 96 and 160 beats per minute

Example 3

A cereal bar has 420 kJ of energy. Walking uses about 15 kJ every minute. How long must you walk to use the energy in the bar?

  1. How many lots of 15 kJ are in 420 kJ? 420 ÷ 15 = 28
  2. So about 28 minutes of walking.

Answer: 28 minutes

Example 4

Leo, aged 9, goes to bed at 8:30 pm and wakes at 7:00 am. How long does he sleep? Is it enough?

  1. From 8:30 pm to midnight is 3½ hours.
  2. From midnight to 7:00 am is 7 hours.
  3. Add them up. That is within the 9 to 12 hours a 9-year-old needs. 3½ + 7 = 10½ hours

Answer: 10½ hours; yes, children need about 9 to 12 hours