The causes of obesity - genes, behaviour and the environment Simply put, obesity is the result of taking in more calories through your diet than you are burning through physical activity.dietphysical activity The reasons for this calorie imbalance vary from person to person. It can be caused by a combination of genes, environment and behaviour. And some drugs and diseases can also contribute to weight gain.genesenvironment behaviour
How calorie balance is controlled In ten years, an average person eats about 10 million calories but their weight typically only changes by about 10 pounds either way. So in most cases, our weight remains stable over time. This is because our bodies control our calorie balance very precisely; much like a thermostat keeps the temperature of a room steady. Our genes and our environment both affect the setting of this weight thermostat and can cause a calorie imbalance. For example, our genes can affect the amounts and types of food that we prefer to eat. And our environment affects the amounts and types of food that are available to eat. So most of the time, our body weight is controlled by instinctive drives. This is why it is incorrect to say that obesity is simply due to a lack of willpower. This is an overly simple way of looking at a very complex condition. And it can make obese people feel guilty or stigmatised.
Obesity is becoming more and more common. For example, the numbers of obese people in the UK have tripled in the last 25 years. This is due to changes in lifestyle, particularly changes in the foods that are available and the amount of physical activity that people take. Food tastes better, is available in more varieties, and is cheaper, especially processed foods. Portion sizes are getting bigger, usually at very little extra cost. For convenience, more people are eating pre-packaged food, fast food and soft drinks, which are often high in calories, fat, salt and sugar. And these types of food are heavily advertised, especially to children. We are also living more inactive lifestyles. The use of cars and public transport over walking and cycling is increasing. Many jobs now involve sitting at a desk for several hours. And inactive pastimes, such as watching television and surfing the internet, are becoming more popular. Cancer Research UK believes that we need a comprehensive strategy to halt the rise in obesity in the UK population, particularly in children and young adults. We need to have an environment that encourages healthy eating and physical activity.
Whatever the environment, some people stay thin and some become obese. Research shows that obesity tends to run in families. Studies with twins and adopted children have shown that genes, rather than shared lifestyles, play a key role in this. Obesity-related genes could affect how we metabolise food or store fat. They could also affect our behaviour, making us inclined towards lifestyle choices that increase our risk of being obese: Some genes may control appetite, making us less able to sense when we are full. Some genes may make us more responsive to the taste, smell or sight of food. Some genes may affect our sense of taste, giving us preferences for high fat foods, or putting us off healthy foods. Some genes may make us less likely to engage in physical activity. People with obesity-related genes are not destined to be obese. But they will have a higher risk of obesity. In the modern environment, they may need to work harder than others to maintain a healthy body weight by making long-term, sustained lifestyle changes.
Behaviour We cannot alter our genetic make-up and it is very difficult to control our environment. But we can learn how to control the lifestyle choices we make. Because our calorie balance is controlled by instinctive drives, short-term quick fix solutions (including most diet programmes) eventually fail. Instead, we must make long- term lifestyle decisions including healthy eating and regular physical activity to reduce our risk of being obese.healthy eatingphysical activity This in turn will reduce our risk of cancer, heart disease, diabetes and several other major diseases. Even relatively small losses, such as 10% of our total weight, can have positive effects on our health.
Check your BMI!! The Body Mass Index (BMI) is a useful tool for finding out if you have a healthy weight for your height. But remember it is only a guide. You can also use our handy BMI chart to find out if you are underweight, overweight or just right. The chart has already done the calculations for you. It shows the underweight, healthy, overweight and obese ranges for various weights and heights. Just find the point where your weight (going across) meets your height (going up).
Calculating BMI To calculate your BMI value exactly, divide your weight (in kilograms) by the square of your height (in metres). This number tells you how healthy your weight is: under 18.5 is underweight is healthy weight is overweight is obese over 35 is very obese.
Body weight – controlling your portion sizes o maintain a healthy body weight, we need to balance the energy we take in from food with the energy that we use up through activity. In the UK, unhealthy diets and inactivity are tipping this balance and leading to higher levels of obesity. The food we are eating is part of the problem - often, it is loaded with fat and sugar so you only need to eat a little to get more energy than you need. The extra, unused energy leads to weight gain. But in many cases, people are simply eating larger portions than ever before.
More and more food It is very easy and tempting to eat too much food. In the last few decades, the portion sizes of food sold in shops and served in restaurants has grown tremendously. A study by the World Cancer Research Fund (WCRF) found that burgers have doubled in size since And pasta servings are about five times larger. Larger portions set up a vicious cycle. People who eat larger meals are used to seeing bigger portions of foods and get stuck in the habit of eating lots of calories that they don't burn off. Research has shown that people eat more if they are given a larger portion of food than they would normally have. You cant always rely on your body to register all those extra calories and adjust your appetite throughout the day. So to stop yourself putting more weight on and maybe lose some weight, you will need to keep an eye on the amount of food you eat, and think about cutting it down. Here are our ideas for being portion-savvy.
At home Eat off a smaller plate - you are more likely to eat less food. Fill your plate up with lots of vegetables (except for potatoes). They are low in calories, good for you, and will help to fill you up.vegetables Be careful when you read food labels. A portion of food as defined by the manufacturer may not be the same as a healthy-sized portion.food labels Cook smaller quantities of food. This will reduce the temptation for second-helpings. After youve served yourself, refrigerate or freeze leftovers so that youre not tempted to have seconds. Use smaller amounts of spreads or fillings and choose low fat varieties. Dont eat from the bag - place foods in a bowl so you can see how much youre eating.
Eating Out If youre eating out at night, think about what you eat during the rest of the day. Dont skip meals - this might make you overeat later. Instead, plan to eat lighter meals earlier on in the day so you dont take in too many calories. Have a salad as a starter. And dont commit yourself to ordering a dessert until youve finished your main course. If youre eating a meal with lots of dishes, like tapas or dim sum, be careful how many you order. If you have a choice, order regular portion sizes instead of large ones. Try splitting a starter or side dishes with a friend - its sociable and will cut down on your calorie intake. Do not feel you have to clear your plate. It can help to decide in advance what youre going to eat and push the rest to the side of the plate. Ask for food the way you want it. You could for example, ask for sauces on the side. These can be high in fat, so you can get more control over how much you put on your meal.
How to avoid hidden calories Our everyday diets may contain sources of calories that we dont take into account. And some 'energy dense' foods have very many calories in a small amount. These hidden calories all add up and can cancel out the positive steps that you may be making elsewhere in your diet. This page contains information on some of the more common sources of hidden calories, and ways of avoiding them.
Fatty Foods It is easy to overeat on foods like butter or spreads, salad dressings, mayonnaise, cheese, pastries, chips, biscuits and crisps. This is because high fat foods contain a lot of energy, even in small portions. So without actually eating large amounts of food, you could be eating more calories than you can burn every day. And because youve not eaten that much, you may still feel hungry.
Eating lots of food high in saturated fat may also increase your risk of cancer.saturated fat Eating less high fat food and choosing reduced fat food where possible will help to reduce your calorie intake. This will also benefit your heart health. Go for semi-skimmed or skimmed milk and choose reduced fat versions of dairy products like spreads, yogurts, cheese, fromage frais, and custard. Changing to semi-skimmed milk could save you 60 calories a day or 420 calories a week. Use a minimum amount of oil when cooking. Spread margarine or butter thinly on your bread, even low fat versions. If possible stop using them entirely. Try to cut down on food that has been cooked in lots of oil or batter. For example, try steamed fish instead of fried fish, bruschetta instead of garlic bread and steamed rice instead of egg fried rice. Cut back on, or better still, cut out pastries, chips, pork pies, sausage rolls, cakes and puddings except for special treats. Try to avoid sauces based on cream or coconut milk. For example, you could have tandoori instead of a korma, a stir-fry or steamed Thai dish instead of a green curry, or a marinara instead of a carbonara.
Salads and vegetarian food Many people see salads and vegetarian dishes as being automatically healthy. It is true that they are a good way of getting some fruit and vegetable portions into your meals. But pay attention to the ingredients and dressings - they can often be loaded with fat and sugar.fruit and vegetable portions Try to avoid salads with high fat, creamy dressings, or ones that contain fatty ingredients like bacon, cheese or croutons. And cut down on vegetarian food that includes high fat ingredients like coconut milk, batter, and full fat dairy products like cheese or butter.
Portion sizes You may be eating too much food without realising it, especially since portion sizes have grown dramatically in recent years.
Lower-fat foods Be careful when reading claims on food packaging - they can be misleading. Diet, light or lower fat foods can have less fat than a similar product but they can still be high in calories, fat and sugar. For example, low fat sausages, spreads and crisps are still high in fat compared to other foods. Reduced fat biscuits can still be high in sugar and calories even though the fat content has been reduced. And remember that foods claiming to be 80% fat-free still have a 20% fat content - thats still quite high!
Soft drinks Drinks are not calorie-free. Many soft drinks (including fizzy and sweetened soft drinks) contain a lot of sugar. These drinks are said to have lots of empty calories - they can contribute to weight gain but dont have much nutritional value. You could aim to cut down on these types of drink. You should drink 6-8 cups of non-alcoholic liquid each day, such as water or low-sugar squashes. Unsweetened fruit juice contains lots of vitamins and minerals, and can count towards your five daily portions of fruit and vegetables. But they are low in fibre and high in natural sugar, so they should only count for one of these portions on any one day.five daily portions
Coffee High street coffee shops are becoming more popular, and offer a wide choice of drinks. Large drinks with lots of cream, milk or sugar can be loaded with fat and calories. Try buying smaller sizes, and asking for skinny drinks that use skimmed milk. Try to avoid cream, flavoured syrup or sugary toppings. Use skimmed or semi-skimmed milk if youre making hot drinks at home too.
Alcohol Drinks Alcoholic drinks are very high in calories. So if you want to lose weight, youll need to consider reducing the amount you drink. Alcohol also increases your appetite - some people notice that they tend to eat more when they drink alcohol. Choose dry versions of all alcoholic drinks - for example dry cider or dry white wine - as these are lower in calories than sweet versions. Opt for low-calorie mixers where you can. Heavy drinking also increases your risk of many cancers, especially if you smoke as well. Our Alcohol section has more information on the links between alcohol and cancer.Alcohol
Physical activity and exercise Just 30 minutes of moderate activity a day, five days a week, can have a positive effect on your health. And the more active you are, the more you can reduce your risk of cancer.
Physical activity and exercise Moderate activity doesn't have to cost you money or too much time. It includes anything that leaves you warm and slightly out of breath, such as brisk walking, gardening, dancing or housework. Even small bits of activity are beneficial, and can add up over the course of a day. It sounds like a cliche, but you can increase the amount of activity you do by making small changes like taking the stairs instead of the lift, or walking some of the way to work, school or the shops. Even if you have been inactive for years, becoming more active now will have a positive effect on your health.
Fitness vs Health Being moderately active will help improve your health and reduce your risk of disease. But if you want to become physically fit you will usually need to do some regular moderate-high intensity activity.
Physical activity tips – Keep on moving Most people in the UK spend long amounts of time sitting down. At work, many of us have jobs where we sit at a desk all day. At home, we are spending more time doing sedentary activities like watching television, surfing the Internet or reading. Spending long periods of time sitting down can contribute to weight gain. But breaking up the time you spend sitting will help you control your weight.
Even small bits of activity are good for you People often feel that they dont have enough time to be more active. And for many of us, it is indeed difficult to find a large block of time to devote to activity. But activity need not be done in a single energetic bout - frequent, smaller movements can also be beneficial to your health. You can be more active each day by doing bits of housework like cleaning or washing, doing chores like putting the rubbish out, changing your working day so you spend less time sitting down, or even fidgeting. When it comes to activity, every little bit counts if it means you are sitting less. Incorporating small changes into your lifestyle will increase the amount of movement and activity you do each day. If you lead a very inactive lifestyle, your first goal should be to reduce the amount of time you spend sitting down. Try and seize the small opportunities to work a bit more activity into your schedule. Here are some tips for doing this:
At home Dont use the remote control, get up and turn the channel over using the TV set. Stand up for 10mins in every hour of watching TV, do the ironing or put the washing away. This will burn extra calories each hour than just sitting. Stand and wash the dishes after each meal, rather than letting a days worth build up. Break up your sitting time by doing your chores like putting the rubbish out or doing the washing up. Some activities can be done in front of a TV, including lifting free weights, stretching or rope skipping. Try learning how to juggle - its both light exercise and a nice party trick.
Getting around Stand on the bus or train, rather than sitting. This burns an extra 70 calories for every hour of travelling.