Healthy Eating

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Healthy Eating
Weight Problems
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A healthy diet contains the right balance of different foods that you might need and the right amount of energy.  A healthy diet contains:

  • carbohydrates
  • proteins
  • fats
  • vitamins
  • minerals
  • fibre
  • water

If your diet is not balanced you are malnourished.  This may lead to you becoming too fat or too thin.  It may also lead to deficiency diseases.  The baby in the photograph is suffering from the deficiency disease kwashiorkor caused by insufficient protein in the diet.  The thinning of the hair and swelling of the cheeks are signs of this.  The swollen areas around the baby's lips are signs of vitamin B deficiency as well.


The metabolic rate

This is the rate at which chemical reactions in the cells of the body are carried out (in particular, respiration) and varies with the amount of activity you do and the proportion of muscle to fat you have in the body.  For example, a person who has lots of muscle will have a higher metabolic rate than a person of equal weight who has more fat.

The less exercise you take and the warmer it is, the less food you need.  People who exercise reuglarly are usually fitter than people who take little exercise.  If you exercise you metabolic rate will normally remain high for some time after you have finished.



Weight Problems

In the developed world too much food and too little exercise are leading to high levels of obesity.  The following diseases are also linked to excess body weight:

  • arthritis (worn joints - excess body weight applies more pressure on the joints)
  • diabetes (high blood sugar)
  • high blood pressure
  • heart disease.

Similarly some people in the developed world suffer from the eating disorder anorexia nervosa in which they have an obsessive fear of gaining weight.

Too little food is a serious problem in parts of the developing world and people suffer from starvation.  People become bery thin and their muscles waste away.  Other symptoms of starvation include:

  • reduced resistance to infection as your immune system cannot work properly
  • irregular (or no) periods in women

You will lose body mass when the energy content of the food you eat is less than the amount of energy that the body needs.  Exercise increases the amount of energy that your body uses.  If you exercise regularly, your body will gain more muscle tissue.  Muscle tissue has a higher metabolic rate than fat tissue.  Therefore athletes have to eat more food to supply the energy they need than people who have more fat tissue.  The less exercise you take, the less food you need.


Cholesterol and Fats

Cholesterol is made by the liver and found in the blood.  You can also get cholesterol through the food you eat, this is called dietary cholesterol. The amount of cholesterol made by the liver depends on a combination of diet (more cholesterol in your diet means less cholesterol will be made by the liver) and inherited factors.  High levels of cholesterol in the blood increases the risk of heart disease and build up of cholesterol in the blood vessels.  The diagrams below show how cholesterol can build up in arteries.  This causes them to narrow and as a consequence your blood pressure will rise.  Pieces of plaque (cholesterol) can cause strokes if they are dislodged from an artery wall and transported to the brain where they can obstruct the flow of blood.


The negative effects of cholesterol are well known.  However, cholesterol is essential to make bile, cell membranes and certain hormones such as testosterone and oestrogen.  It belongs to a class of molecules called steroids.

Cholesterol cannot dissolve and in the blood and has to be carried around your body by lipoproteins.  There are two types of lipoprotein:  Low-Density Lipoproteins (LDLs) are 'bad' cholesterol and can cause heart disease.  High-Density Lipoproteins (HDLs) are 'good' cholesterol.  Many medical experts think HDLs carry cholesterol away from the arteries and back to the liver where it is removed from the blood.  Balancing the levels of HDLs and LDLs is very important to good heart health.

Saturated fats, found in animal fats like meat, butter and cheese, increase blood cholesterol levels.  Monounsaturated and polyunsaturated fats both help to reduce blood cholesterol levels and help to improve the balance between HDLs and LDLs.  Monounsaturated fats are found in foods like olive oil and peanuts.  Polyunsaturated fats are found in sunflower oil and many margarines.


Statins are drugs that can lower the amount of cholesterol in the blood.  This can decrease the risk of heart attacks or strokes.  Oyster mushrooms contain naturally occuring statins.  Liver damage is a side-effect that has been associated with the use of statins.  Around one in three people over the age of 40 regularly take statins in England. A review of their effectiveness suggest they have little effect at protecting people who are not already at a high risk of heart disease [If you are interested in finding out more see the Daily Telegraph]


Salt is an essential part of your diet and without it your nervous system would not work properly and you would also upset many chemical processes in the body.  However, too much salt in the diet can lead to increased blood pressure for about 30% of the population.  Processed foods often contain a high proportion of fat and/or salt.  You can control your salt intake by doing your own cooking and reading food labels carefully to check for the levels of salt and saturated fat.


Revision Activities

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