Editorials

The obesity epidemic in young children

Reduce television viewing and promote playing

Papers p 326

A rapid increase in the prevalence of obesity in children has been seen in England, the United States, and around the world.^1-3 In this issue of the BMJ, Bundred and colleagues report that among 3 to 4 year old English children there was a 60% increase in the prevalence of being overweight (having a body mass index >85th centile) and a 70% increase in the prevalence of obesity (body mass index >95th centile) between 1989 and 1998.⁴ Growth data were standardised for age and sex using the British Growth Reference Charts, and the analyses seem sound. The surprising finding in this study is that the increases in the prevalence of obesity are occurring among such young children.

Given what we know about the natural history of being overweight in childhood and obesity in children these findings should heighten concern. Although the risk of obesity in adulthood is not increased among children who are overweight at 1 and 3 years old, the risk rises steadily thereafter regardless of parental weight.⁵ Furthermore, more than 60% of overweight children have at least one additional risk factor for cardiovascular disease, such as raised blood pressure, hyperlipidaemia, or hyperinsulinaemia, and more than 20% have two or more risk factors.⁶ Type 2 diabetes, which was previously rare in children and adolescents, now accounts for over 30% of new cases in some parts of the United States; most cases of type 2 diabetes in children and adolescents are attributable to obesity.⁷ Therefore, Bundred et al's data herald a further increase in the prevalence of adult obesity.

Identifying the causes of the rapid increase in the prevalence of obesity among young children is a critical challenge. Increased birth weight increases the risk of obesity later,⁸ but children with low birth weights tend to remain small into adulthood.⁹ However, as Bundred and colleagues show, only modest increases in birth weight occurred among infants, suggesting that changes in birth weight did not account for the changes in the prevalence of obesity among older children. Because the gene pool did not change substantially between 1989 and 1998, the rapid increases in obesity must reflect environmental changes.

Factors that promote an increase in energy intake or a reduction in energy expenditure cause obesity. In the United States in the past 30 years important changes have occurred in family eating patterns and in the consumption of fast foods, pre-prepared meals, and fizzy drinks. Likewise, the amount of physical activity that children engage in has been reduced by an increase in the use of cars, an increase in the amount of time spent watching television, and a decrease in the opportunities in many communities for physical activity on the way to school or in school. Although television viewing seems to cause obesity in children in the United States it is not clear how many of these other factors promote obesity in young children.¹⁰

Both food intake and activity in young children are strongly influenced by parents. Although controversy still exists, breast feeding seems to lower the risk of later obesity.¹¹ In early childhood, the more parents encourage children to eat certain foods the less likely they are to do so.¹² Thus, foods that have been forbidden may be overconsumed when children finally have access to them.¹³ Children of mothers who exert a high level of control over their food intake become less able to regulate their own intake, although a mother's reaction may occur secondary to her children's inability to control their own food intake.¹⁴ Children who eat meals with their family consume more fruits and vegetables, fewer fizzy drinks, and less fat in food both at home and away from home.¹⁵ Television advertising of food directed at young children may help explain why reduced television viewing reduces rates of weight gain.¹⁶

Promoting breast feeding, implementing regular family meals, restoring to parents the responsibility for what children are offered, and restoring to children the choice of whether to eat what is offered, are logical nutritional interventions that are likely to reduce young children's access to foods that are high in calories. Opportunities for spontaneous play may be the only requirement that young children need to increase their physical activity. Reducing the amount of time that children are allowed to watch television is one strategy that offers children opportunities for activity, and it is likely to alter requests for advertised foods as well.

These are not novel approaches; a generation ago, because there were few alternatives, these practices were the norm. Although there is no data to show that these interventions prevent obesity, none of these interventions are likely to have adverse effects, and all of these interventions will improve the quality of family life. Strategies to change families' patterns of eating and activity must be adapted to the social and economic pressures of today's world. However, in view of the rapid increase in the prevalence of obesity and its implications for chronic disease, a return to basics seems to be essential.

William H Dietz, director. 

Division of Nutrition and Physical Activity, Centers for Disease Control and Prevention, 4770 Buford Hwy NE, Mailstop K-24, Atlanta, GA 30341, USA (wcd4{at}cdc.gov)