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Childhood Obesity - Causes, Consequences & Prevention

Almost one in five children are overweight or obese when they start primary school, and this rises to one in three at the start of secondary school.

Children who carry too much fat are five times more likely to grow up to be overweight adults with an increased risk of conditions such as heart disease, Type 2 diabetes, and cancer. What’s more, being overweight can also impact on their self-esteem and emotional wellbeing.

Is your child overweight?

It’s sometimes hard to tell if a child is overweight, especially in the early stages of weight gain. Body mass index (BMI), a measure that uses height and weight, is a reliable way of telling if an adult is a healthy weight. But adult BMI charts don’t work for children when they’re growing – and they all grow at different rates. Also, it’s not unusual for children to carry bit of ‘puppy fat’ before they have a growth spurt.   

How to calculate weight using a child’s BMI chart

For children, doctors therefore use a different measurement method called child BMI centile charts, which compare your child with a number of other children of the same age and gender. The entire weight range for a particular age is divided into 100 categories. If a child’s weight falls into the top nine categories, they are classed as overweight. If it falls into the top two categories, they are classed as obese, or very overweight.

Signs your child may be overweight or obese

As it can be hard to tell if your child is overweight (or is at risk of becoming overweight or obese), it‘s important to recognise the warning signs. Here are a few to look out for:

  • They’re noticeably bigger than lots of children in their age group

  • They wear clothes that are made for children older than them, especially if they need clothes two sizes up

  • If they regularly eat the same sized portions as adults in your family, they could be at risk

  • They could also be at risk of becoming overweight if you notice that they seem to get fatigued easily and find it hard to keep up with other children during physical activities 

If you’re concerned about your child’s weight, it’s a good idea to check with your GP, practice nurse, or health visitor.

Health risks and consequences for overweight children

Children who put on too much weight are at increased risk of developing a number of different health conditions in the future. Childhood obesity can have long term consequences, these include:

  • Cardiovascular, or circulatory, problems including heart disease, high blood pressure, high cholesterol levels and stroke

  • Type 2 diabetes

  • Many forms of cancer, including colon and breast cancer – it’s estimated that being overweight is the cause of 5% of cancers in the UK

  • Osteoarthritis, or wear and tear on the joints

Many doctors say that being overweight is already causing some children to show signs of conditions, such as high blood pressure and Type 2 diabetes, which don’t normally appear until adulthood. Overweight or obese children can also be more prone to mental and emotional health problems. They may be bullied or teased by other children and can suffer from low self-esteem.

What causes childhood obesity?

The simple answer is that children put on too much weight when they are regularly taking in more calories than they’re burning off. There are lots of reasons for this.

An ‘obesogenic environment’ – many of us live in an environment that encourages us to lead an unhealthy lifestyle. For example, dangerous roads and a general lack of time mean that many children are driven to school rather than walking or cycling

Dietary factors – eating too much high-carbohydrate, fatty, and sugary food. Common culprits are fast foods, sweetened breakfast cereals, and sugary drinks, including fruit juice. The National Diet and Nutrition Survey has found that kids eat twice as much sugar as they should. Portion sizes can also be an issue, if a child is regularly served adult-sized portions or is pressured to ‘clear their plate’.

Lack of exercise – the 2018-19 Sport England Active Lives Survey showed that only 47% of children met the government’s recommendation of an average of an hour’s physical activity a day.

Too much screen time – a study by Cancer Research UK found that children who spend a lot of time online or watching TV are more likely to be overweight. As well as getting less exercise, they’re exposed to lots of junk food adverts, and may tend to snack while they’re watching without really thinking about it.

Being overweight runs in the family – children are more likely to become overweight or obese if they have an overweight parent. Genetic factors can mean some of us have bigger appetites and tend to gain weight more easily, but family lifestyle habits often play a part too.

Emotional problems – a study by the University of Liverpool found that obesity and emotional problems are closely connected. As with adults, if children are feeling sad or stressed they are more likely to seek comfort in food and because being overweight can have a negative effect on mental health, this can turn into a vicious cycle.

The COVID-19 pandemic has had a negative impact on many children’s activities, social lives and mental health. If you’re concerned about your child, read our tips on how to spot the signs of poor mental health in children

How to help your child stay a healthy weight and prevent child obesity

If you are wondering what can you do to avoid avoid childhood obesity, here are some ways you can help prevent your children or grandchildren becoming overweight:

  • Encourage them to eat a healthy diet, including at least five portions of fruit or vegetables a day. If you struggle to get them to eat a wide range of foods, check out our article on how to help fussy eaters.

  • Substitute sugary drinks with water and low-fat milks. Gradually dilute drinks such as juices to wean them off the sweet taste.

  • Make sure portions aren’t too big. As a general rule, a suitable portion for a child should fit into the palm of their hand. If in doubt, it’s best to start with a small serving as the child can always ask for a bit more if they’re still hungry. Using smaller plates rather than adult-sized ones will also help reduce portion sizes.

  • Don’t try to make your child eat everything on their plate if they say they’re full. This will override their natural appetite control and encourage them to eat when they’re not hungry.

  • Encourage your child to get plenty of exercise. Read our article if you need some ideas for getting kids active.

Find more tips on how to keep your child at a healthy weight

Tackling childhood obesity in a positive way

Finally, remember that too much focus on weight can backfire and cause children to feel guilty and develop a negative body image. Make sure your child understands that it’s normal for people to come in different shapes and sizes, and that very few of us can achieve the ‘ideal’ bodies we see all the time in the media. Frame discussions about diet and weight in terms of being healthy, feeling good and taking care of ourselves.

Useful links

You can find lots of diet and health information for children on the NHS change 4 life website 

Find more about BMI centile charts for children 

Medically reviewed by Cheryl Lythgoe on 28th June 2021. Next review date: 28th June 2022.