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Citrus fruit and dumbbells.

What factors affect a person’s weight?

Most people can tell you that if you want to lose weight you need to eat less food and do more exercise. This advice is quite correct, based on the principle that the body responds to its energy balance.

Diet and exercise and energy balance

Energy is taken into the body as food, and energy is lost in undertaking body functions and in movement and exercise. Any energy in excess of what is needed will be stored mainly as body fat. Any energy deficit will be made up by burning energy from body stores.

If the principle of energy balance is so simple, then why is it so hard for people to lose weight?

Many, many different factors can affect our energy balance. We can think about them under two headings: the inherited factors and the environmental factors.

Inherited factors and body weight

Our genetic inheritance can affect how easily we gain or lose weight. All people are different. Some people will move around more than others and use up more energy. Some people absorb their food a little more efficiently than others. Some people have a stronger craving for fatty, sweet foods than others.

So even in societies where conditions make it hard to become overweight you will see people of different size and body shape due to these inherited differences.

Some people will be just a bit larger, some people will be just a bit smaller.

Environmental factors

In Westernised societies all over the world, people are now getting steadily more and more overweight. This change is happening very quickly. It has happened over just 20 or 30 years. This is much too fast to be explained by a change in our genes, so we must look for explanations in changes that have happened in our environment. What are the triggers that are causing us to eat more and to exercise less? It is here that we can understand why it is so hard to lose weight.

Environmental factors and food intake

Energy intake is stimulated by the presence of food and by high food variety. Food in Westernised societies is now plentiful, affordable and always all around us. How many restaurants, food outlets and shops selling food do you see every day on your way to work or school? How many glossy advertisements for food would you see? How many appealing kinds of snack food are sold in your local supermarket?

A lot of the foods that are strongly advertised are energy dense foods - food (or drink) that supplies many calories in every gram, ounce or cup. Choosing energy dense foods makes it much easier to consume more energy than you really need so that you readily gain weight.

Technical advances in agricultural food production, food distribution and food manufacturing has made many foods that were once scarce –only eaten as special treats and at festive events-have now become very common and quite cheap. Foods such as chocolate, beef steak, ice-cream, sweet cookies and cakes, soda drinks, candy; these rich foods can now be eaten every day.

Food manufacturers have also learned that they can make more money from selling foods as large sized items rather than in smaller amounts. Over the decades, the portion size of many ready-to-eat foods has increased considerable. This encourages over-eating as so many of us have grown up being told not to waste food and to eat up everything on our plate.

Healthy choices

Often people are told to just carefully select healthy food and they will lose weight. But how easy is it to do this? Have a look at your local supermarket. How many healthy foods do you see? How many are unhealthy? How many foods are loudly advertised as healthy choices when really they are high in calories? Now take a look at the places where people buy their lunch. What is the food choice like?

Very often you will find that the main foods for sale are not salads, fruit and whole grain breads and cereal products but energy dense chips and fried foods, pasta covered in cheese, rice dishes heavy with oil, sugary cakes and biscuits.

A food supply that does not emphasise healthy choices is one which makes it much harder for people to lose weight.

Weight loss and exercise

Weight loss is aided by an active lifestyle with regular exercise. But how easy is it for people to be active in Westernised societies? We often travel by car and do not walk far. Even if we want to walk or cycle there may not be any walking tracks, good pavements (sidewalks) or bicycle paths that are safe and away from the traffic. You may not feel safe out walking when it is getting dark. You may think walking is a good idea, but you have no time to fit it into your busy work day.

For many of us, work or at school involves long periods sitting often looking at a screen. We are very busy but we are very inactive. Our opportunities for relaxation then often involve even more sitting- watching TV or another kind of screen.

In addition, many of the domestic tasks that used to require labour have now been mechanised. We have dishwashers, washing machines, vacuum-cleaners, lawn mowers, electric hedge clippers- even TV remote controls.

Our everyday environment no long requires us to exert much energy.

Environmental change

So when you think about our food environment and our physical environment you can see that there are many factors acting on us that make it difficult to lose weight - and instead are causing many people to continually gain weight.

Some people are more influenced by one factor than other. For one person the problem will be that they spend far too much time sitting, for another person it will be the choice of three jam doughnuts as an afternoon snack. So to change outcomes for populations as a whole, many different things need to be addressed.

In the future, public health workers hope that these many environmental factors impacting on our body weight can be improved.

We need to think about how to change our food supply and how to change our built environment in cities and towns, how to change our habits and entertainment, so that it becomes much easier for people to have a healthy lifestyle and control their body weight.


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Food as Medicine

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