Childhood obesity

How do I know if my child is overweight or obese?

Excess weight and obesity are most commonly assessed using body mass index (BMI). You can calculate a child’s BMI using the same method as for adults — their weight in kilograms divided by their height in metres squared (kg/m2). However, because BMI changes with the age and gender of a child, it has to be assessed using an age-adjusted chart or a BMI calculator specifically for children. Children above the 85th percentile are classed as overweight and those above the 95th percentile are classed as obese. If you are told that your child’s BMI is in the 85th percentile, this means that 85 per cent of other children of the same age and sex will have a lower BMI than your child.

Is it lifestyle or genetics?

Obesity in children is caused by a number of interacting factors. Certain metabolic and hormonal disorders, some of which are genetic, can cause obesity in children. However, these conditions are rare. Aside from these disorders, it also seems that genetic factors contribute to a child’s tendency to become overweight.

The main external influence on weight gain, however, is energy imbalance. When our energy intake (the food we eat) is roughly equal to the energy we expend (or burn), we maintain a fairly constant weight. When the balance moves towards more food or too much unhealthy food, we gain weight; when it moves towards greater energy expenditure or reduced energy intake, we lose weight. Our increasing consumption of energy-dense (high-calorie) foods high in sugars and saturated fats, combined with reduced physical activity, has led to a so-called obesity ‘epidemic’.

Many children no longer walk to school, and interactive game consoles, PCs and extensive television viewing are gradually replacing regular outdoor activity. Other factors, such as more frequent eating out in restaurants or eating fewer meals as a family are increasing the quantity and reducing the quality of the food we eat.

Are there any health problems associated with being overweight or obese in childhood?

There are both short-term and long-term health problems associated with obesity in childhood. As well as the physical discomfort of being overweight, children can experience bone and joint problems as well as suffer from asthma or shortness of breath on exertion, heat intolerance and tiredness. They can also develop high blood pressure, abnormal blood fat levels and type 2 diabetes. A large proportion of obese children also suffer from obstructive sleep apnoea (episodes of disturbed breathing during sleep) which can lead to problems with concentration and learning performance.

Obesity in childhood increases the risk of being obese as an adult. Overweight and obese children are at increased risk of health problems such as heart disease, stroke, diabetes, osteoarthritis and several types of cancer once they reach adulthood.

Obese children can experience social and psychological distress related to how they are treated by other children, how they perform at sports and how they look. They can experience psychosocial problems, usually associated with a negative self-image and, in some cases, low self-esteem. These problems are usually greater in girls and may increase with age. Low self-esteem in childhood can also lead to an increased tendency to smoke and drink alcohol.

How do I manage my child’s weight without affecting their growth?

You can help your child by cutting out sugary drinks and fatty snacks; however, it is important that you don't exclude foods that he or she needs for growth. Adequate quantities of cereals, vegetables, fruits, lean meats (or alternatives such as fish, eggs, beans, pulses and nuts) and dairy foods must always be included in the diet.

Treating obesity

If you think your child is overweight, a proper clinical assessment by your general practitioner is recommended. Depending on the outcome, he or she may suggest a weight-management programme or refer your child to a dietitian or paediatrician for further assessment.

When treating obesity in children, health professionals usually focus on achieving long-term changes in diet and physical activity. Depending on the child’s age, this approach aims to slow or stop weight gain rather than meet a target weight and generally involves:

  • reducing energy intake, for example, using low-fat dairy products and increasing consumption of fruit and vegetables;
  • increasing physical activity including incidental activity (for example, walking to and from school) as well as formal exercise programmes;
  • decreasing sedentary activity, for example, limiting the number of hours spent watching television or playing PC or video games to a maximum 2 hours per day;
  • family involvement, for example, changing shopping and cooking practices and altering attitudes towards snacking and mealtimes; and
  • behaviour modification, for example, making time to eat breakfast, reducing the volume of soft drinks or fruit juices drunk or taking a packed lunch to school.

Family support for eating and behaviour change in overweight and obese children is extremely important. Research has shown that when the family is included in the treatment programme, long-term success rates are much higher than when they are not.

There are no medicines currently licensed for the treatment of obesity in children.

Encouraging healthy eating outside the home

With young children, it is relatively easy to control their food intake and exercise. As children start primary school and eventually move on to high school, they are increasingly subject to peer pressure and have access to a wider variety of food. However, you can always encourage a healthy and responsible attitude towards food and exercise. For adolescents, this may include involving them in meal choice and preparation; praising their healthy food choices but limiting criticism of less healthy ones; and helping them gain confidence in managing other aspects of their life before they have to take charge of their weight.

Being a good role model

Obese children are at great risk of obesity in adulthood so good lifestyle habits need to be introduced as early as possible. As parents, you can help everyone in your family make healthier food choices and be more active just by showing how it’s done. Having a family-focused approach can help children make sustainable lifestyle changes that can improve health and prevent future disease.


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2. World Health Organization. Global strategy on diet, physical activity and health. Childhood overweight and obesity. (accessed Apr 2012).
3. Obesity in children (revised June 2009). In: eTG complete. Melbourne: Therapeutic Guidelines Limited; 2012 Mar. (accessed Apr 2012).
4. Centers for Disease Control and Prevention. About BMI for children and teens (updated 13 Sep 2013). (accessed May 2012).
5. Centers for Disease Control and Prevention. About BMI for children and teens (updated 15 Sep 2013). (accessed May 2012).