Obesity is an increasing problem in childhood and 1 in 10 children are obese even by the time they start primary school. Most overweight and obese children have nutritional obesity, and the diagnosis can be made clinically, as rare causes are accompanied by poor growth and other clinical features such as learning disability and dysmorphic features. In the UK overweight is defined as a body mass index (BMI) above the 91st centile and obesity as BMI above the 98th centile.

At one time obesity in childhood was thought to be a cosmetic problem, but it is now clear that comorbidity can occur in children and adolescents too. The mainstay of management is lifestyle change. Lipase inhibitors to induce fat malabsorption and bariatric surgery are occasionally considered in adolescents.

Nutritional Obesity

The metabolic factors that predispose some individuals to becoming obese have yet to be determined and the correlation between nutrient intake and development of obesity is not simple. Nutritionally obese children are tall, but as they tend to develop puberty early, their final adult height is not necessarily tall. Despite its prevalence, obesity remains a stigma and obese children have a high incidence of emotional and behavioural difficulties.

Lifestyle change is difficult to achieve and it is now well recognized that traditional dietary advice that focuses on the child is not effective. Guidance needs to be holistic, family focused and delivered in a skilled way that builds motivation. It includes the following.

• Support. Obese children are often the victims of teasing by peers and psychological disturbance is common. Even if weight control is not successful, continuous support is necessary to help these children cope with their condition.
  
• Encouraging physical activity and reducing sedentary behaviour. This may be difficult if obese children experience ridicule when trying to be active.
  
• A balanced healthy diet. Rapid decreases in weight through ‘crash dieting’ should not be attempted and, while the child is growing, weight maintenance is a reasonable goal.
  
• Monitoring of comorbidity and management when needed.
  
• Medication and surgery are generally not appropriate or licensed (although may be considered in older adolescents with comor­bidity).

Most obese children can be managed in primary care or the community, although those with complex difficulties should be under the care of a paediatrician and multidisciplinary team. Group programmes providing lifestyle education and opportunities for physical activity are increasingly available.

Despite medical intervention, reduction of obesity once it is well established is difficult. Psychological difficulties may well persist into the adult years. Society deals harshly with the obese and studies show that obesity is a handicap later in life. In childhood overt medical complications are few, although metabolic markers for cardiovascular disease, diabetes and fatty liver are common. Obese children are more susceptible to musculoskeletal strain and slipped capital femoral epiphyses. Rarely, insulin-resistant diabetes mellitus develops in childhood. As obese adults, the morbidity is significant with diabetes and hypertension common, leading to early mortality from ischaemic heart disease and strokes. Gallstones and certain cancers are also more prevalent.

Infant Obesity

Excessive weight gain and obesity in infancy are now recognized as being far from benign. Epidemiological studies show that this can track into childhood and on to adult life. When obesity in the early years is extreme, genetic syndromes should be considered, particularly when there is dysmorphism, developmental delay and congenital abnormalities. Health visiting teams are beginning to recognize and address excessive weight gain as a problem as concerning as weight faltering.

Public Health Issues

Prevention

As in most conditions, prevention is better than cure. There is some evidence that breast-feeding in infancy is protective, and promotion of good nutrition in the early years, when food habits are developing, is important. Physical activity needs to be encouraged in all children, not simply the obese. There is a need for these health issues to be addressed in baby clinics and in school, particularly during adolescence when a high intake of high fat foods and decrease in exercise is common. If intervention is provided early in the course of obesity, weight control is likely to be more successful.

Monitoring of Obesity

In the UK the National Child Measurement Programme measures children at entry to primary school (age 4–5 years) and on leaving primary school (age 10–11 years). Parents are notified if their child is overweight or obese.