Discussion

This cross-sectional sample of US children demonstrated concern and were knowledgeable about issues regarding weight, overweight, nutrition, physical activity and related socio-behavioural factors.

When asked to categorize themselves, 27·0 % of children reported being overweight. This compares with a national rate of 34·7 % of 6–19-year-olds with BMI at or above 85th percentile, based on the most recent NHANES data⁽ Reference Ogden, Carroll and Kit ^{2 )}. This finding is in line with those reported in a recent study of seventeen obese 8–12-year-olds in the US Midwest in which 42 % of these overweight children reported that they were underweight or normal weight⁽ Reference Snethen and Broome ^{22 )}. Similar trends have been reported internationally, as demonstrated by a study in China showing that underestimation of childhood overweight is common among both children and mothers in China, particularly for children with the highest BMI⁽ Reference Yao and Hillemeier ^{19 )}, and a European study⁽ Reference Brodsgaard, Wagner and Peitersen ^{23 )} showing that overweight children were less able than normal weight children to correctly assess their own body weight. In the present study 42·9 % of the children had an accurate estimation that approximately one-third of US children are overweight. However, a similar proportion (47·1 %) overestimated, thinking that half or more of US children are overweight. The high percentage of children who overestimated the national rate of overweight, along with self-assessment of overweight at lower than the national rate, may reflect a shift in cultural weight norms among today's children and may be an indication that they see themselves as smaller than their peers or the population around them. A recent study in Italy showed that higher regional obesity prevalence was associated with lower maternal perception of their child's weight status, suggesting that what is common has a greater likelihood of being perceived as normal⁽ Reference Binkin, Spinelli and Baglio ^{24 )}. A similar shift in perception of weight status among US children may explain the findings reported here. Such changes in cultural weight norms and perceptions must be considered when crafting strategies to address the issue of childhood obesity.

A high percentage of children, both those who self-categorized as overweight and under/normal weight, reported worrying about doing well in school and about having enough money. However, when asked how worried they were about being or becoming overweight there was a large difference between children who self-categorized as overweight and those self-categorized as under/normal weight, with 81·9 % of self-categorized overweight children reporting worrying compared with 31·1 % of self-classified under/normal weight children. These results are consistent with a study of Scottish 15-year-olds in which worrying about weight was also found to be more prevalent among obese children⁽ Reference Sweeting, West and Young ^{25 )} and a study in Germany showing that obese children and adolescents had more weight concerns than their normal weight counterparts⁽ Reference Rudolph, Bluher and Falkenberg ^{16 )}. Therefore there are similar concerns in the USA and other countries, and weight status is a significant worry and an additional burden borne by children who consider themselves overweight or obese.

Children overwhelmingly agreed (91·1 %) that it was important to not be overweight at their age and gave both health-related and social-related reasons in open responses. This is in contrast to a literature review performed in the UK which reported that children focused on the social impact of body size rather than health issues⁽ Reference Rees, Oliver and Woodman ^{18 )}. The overwhelming majority of children reported that if someone their weight is overweight they will likely be overweight in adulthood; they will likely get an illness such as diabetes or heart disease in adulthood; they will not be able to play sports well; and they will be teased or made fun of in school. A recent study of 1555 adolescents at two high schools in Connecticut also reported that youth perceive frequent and multiple forms of weight-based victimization⁽ Reference Puhl, Luedicke and Heuer ^{26 )}. The findings reported here show that children have a clear understanding of the long- and short-term negative consequences of being overweight, both now and in the future as adults. This understanding is perhaps the result of public health education and regular exposure to health-related claims and advertising, such as claims associated with food advertising. The findings highlight the potential for children to be an important part of crafting and executing solutions, given that they clearly understand and worry about the long-term implications of being overweight.

When asked to choose three of ten possible choices, children selected eating or drinking too much sugar, candy or soda; consuming too much food; and consuming food with too much fat as the top three reasons for overweight at their age. These food-related choices ranked ahead of parents being overweight or the two physical activity-related options provided (not enough gym or physical education classes at school; not safe to walk or play outside). However one limitation of this question is that a broader physical activity-related response such as ‘lack of exercise/physical activity’ was not one of the choices provided. Children who entered a response that was coded as ‘lack of exercise/physical activity’ had to select ‘something else’ and write into the text box. It is possible that ‘lack of exercise/physical activity’ would have been one of the top three reasons selected if the choices were presented differently. Responses to an open-ended question about what adults need to know to help people their age to be a healthy weight also focused more on food/nutrition than on physical activity. These perceptions are in line with studies showing that in adolescents, increase in moderate physical activity was not associated with change in weight status⁽ Reference Sonneville and Gortmaker ^{27 )}, possibly due to increased dietary intake or body composition changes in response to physical activity⁽ Reference Sonneville and Gortmaker ^{27 ,} Reference Atlantis, Barnes and Singh ^{28 )}. However, an increase in high-intensity physical activity was effective in reducing body fat, although not BMI⁽ Reference Atlantis, Barnes and Singh ^{28 )}. National data suggest that a wide range of strategies, including modifications in dietary intake and physical activity, can be utilized in reducing the imbalance in energy intake and expenditure (energy gap) associated with weight gain⁽ Reference Wang, Gortmaker and Sobol ^{29 )}. The findings reported here show that although children have an understanding of the importance of dietary intake and physical activity in maintaining a healthy weight, there is an opportunity for increased education and awareness of energy balance, and the role of both dietary intake and physical activity.

Children who self-categorized as overweight were more likely to have spoken with someone about their weight over the last year than those who self-categorized as under/normal weight. When they did speak with someone, self-categorized overweight tweens spoke most often with their mothers and self-categorized overweight teens spoke most often with their friends and others of similar age. This is in line with the greater importance placed on peer relationships as children move into teenage years. In addition a significant proportion of self-categorized overweight teens also spoke with their mothers, underscoring mothers’ unique role in promoting healthy eating and activity behaviours to their children⁽ Reference Rocchini ^{14 )}. There was also communication with doctors/nurses and other adults. A high proportion of self-categorized overweight children reported speaking with more than one person about their weight issues over the last year. Therefore children who see themselves as overweight are discussing the issue with trusted individuals, providing opportunities for effective intervention and further underscoring the increased burden borne by overweight children. A recent analysis of NHANES data⁽ Reference Perrin, Skinner and Steiner ^{30 )} showed that less than one-quarter of parents of overweight children reported having been told by their health-care professional that their child is overweight. In addition the choice of terminology used by health-care providers when communicating about children's weight and obesity plays a role in effective motivation to lose weight⁽ Reference Puhl, Peterson and Luedicke ^{31 )}. Therefore the individuals with whom children are speaking need to be well informed and to communicate effectively about the issues.

Analyses of data by race/ethnicity, parental education and urbanicity showed no significant differences. It is possible that differences in weight status did not show up in these analyses partly because weight was self-reported. However, when analysed based on geographic region, a higher proportion of children in the southern part of the USA reported being overweight compared with other regions. This is in line with national data showing the highest obesity rates in the southern part of the USA^{( 5 )}.

Limitations of the present study that must be taken into consideration include the fact that while every effort was made to craft questions carefully, there is the possibility that question design may have influenced responses. In addition, surveys were conducted online and there was no way to ensure that responses were those of children alone and not influenced by parents. To be part of the study an email address was needed and access to a computer, although not necessarily a home computer. Participants could complete the survey at a computer away from the home, e.g. at a public library. In spite of this, online sampling may result in lesser representation from lower-income children who do not have Internet access in the home. While a telephone survey may have generated a more random sample than the online survey, telephone surveys also have limitations such as higher representation of those with land-line telephones in their homes and lower response rates. Telephone surveys are also not age-appropriate, as questions and response options read over the telephone may be more difficult for a child to follow than written questions and response options. Many parents are also reluctant to allow their children to participate in telephone surveys.

Children typically do not participate in large-scale decisions that affect their well-being, which may explain why some past obesity prevention efforts have been unsuccessful. There is a definite lack of studies that capture opinions and concerns of a large cross-section of children about weight, overweight, nutrition and physical activity issues⁽ Reference Rees, Oliver and Woodman ^{18 )}; hence the value and importance of the data presented in the current study. Data reported here show that children have a good understanding of issues regarding weight, overweight, nutrition, physical activity and related socio-behavioural factors. Adding their voices to the evidence base will allow children to have an influence over future policies, interventions and treatment decisions. The incorporation of these data into decision-making processes will help organizations to develop and tailor appropriate programmes.