Regular exercise and a balanced diet are needed to keep the body healthy. Too little food leads to a person being underweight and prone to certain types of illness, while too much food and not enough exercise leads to a person being overweight and other types of ill health.
A mixture of different types of food in the correct amounts is needed to maintain health.
The main food groups are carbohydrates, fats and proteins.
This table summarizes some typical sources of these nutrients and why our bodies need them.
Mineral ions and vitamins are also important in a healthy diet. They are needed in small amounts for healthy functioning of the body.
An imbalanced diet causes a person to become malnourished. For example:
too little food may lead to a person being underweight
too much food may lead to a person being overweight.
A poor diet may also lead to deficiency diseases. For example, too little vitamin D in the diet can lead to rickets, which affects the proper growth of the skeleton. Type 2 diabetes is also a problem related to poor diet. Note that you do not need to know how the nutrients work or the effects of any particular deficiency in the diet for your exam.
If someone’s diet consists of food with a lower energy content than the amount of energy their body uses, the person will lose body mass.
Respiration is a chemical reaction that allows cells to release energy from food. The metabolic rate is the speed at which such chemical reactions take place in the body and varies because of several factors, including age, gender and inherited factors.
Metabolic rate is also affected by the:
proportion of muscle to fat in the body
amount of exercise and other physical activity.
The metabolic rate increases as we exercise and stays high for a while afterwards. People who exercise regularly are usually healthier than people who don't.
A molecular model of a cholesterol...