Growing up in Scotland: overweight and obesity at age 10

7. Summary and concluding remarks

7.1. Summary

Childhood obesity is a significant international public health challenge and with one of the highest levels of childhood obesity amongst OECD countries, it is a particularly significant challenge for Scotland.

Using unique data from GUS, this report has sought to provide further insight into the prevalence of overweight and obesity amongst 10 year old children in Scotland, how this varies between children with different characteristics, whether social and demographic variations in levels of overweight/obesity change between ages 6 and 10, and how individual weight status changes over that period.

Building on the previous analysis undertaken on GUS the report addressed the following questions.

What proportion of children are overweight/obese at age 10, compared with age 6, and what proportion move into and out of healthy weight/overweight/obese categories during that period?

The majority of children are a healthy weight at both ages. However, the findings demonstrate clearly that levels of overweight and obesity increase with age. Whilst at age 6 24% of children were overweight, including 11% who were obese, by age 10 this had increased to 34%, including 19% who were obese. On average, BMI had increased for all children, including those who remained in the same BMI category at both ages. In particular, children who were obese at both time points showed an average BMI increase of 4.8 points whilst children who remained a healthy weight showed an average increase of 1.4 points. Amongst all children the average increase was 2.5 points.

Children who were overweight or obese by age 6 were more likely to remain so or to show an increase in BMI by age 10 than to show a decrease in BMI. Similarly, most children who were a healthy weight at age 6 remained so. This may suggest that tackling or preventing overweight at younger ages will help reduce levels of overweight and obesity and later ages. However, being overweight or obese at age 6 does not inevitably mean having the same status at age 10; a minority of children, particularly amongst those who were overweight rather than obese at age 6, saw their BMI reduce over the period, moving into lower risk categories. Nevertheless, the majority of children who were overweight (not obese) at age 10 had been a healthy weight at age 6, suggesting that preventing and tackling overweight/obesity in early childhood alone would not be sufficient in reducing later levels of overweight/obesity and must be sustained over the primary school period.

How does overweight/obesity vary amongst 10 year old children according to demographic and socio-economic characteristics and is there any change in the social gradient of overweight/obesity between age 6 and age 10?

Levels of overweight and obesity did not differ significantly between boys and girls or between children of white and other ethnicities at either age 6 or age 10. These groups also saw similar levels of increase in the proportion of children who were overweight and obese.

The prevalence of overweight and obesity did vary significantly amongst children in different socio-economic circumstances. For example, at age 10, 25% of children living in the least deprived areas were overweight or obese compared with 39% of children living in the most deprived areas.

An increase in levels of overweight and obesity between ages 6 and 10 was observed across all socio-economic sub-groups. Notably, however, children in more disadvantaged groups were more likely to become overweight or obese during this period than children in more advantaged groups. The result is a widening social inequality in the prevalence of overweight including obesity between age 6 and age 10. This suggests policies aimed at addressing childhood overweight and obesity may benefit from some targeting of children and families at greater risk and tailoring to address the specific issues and circumstances experienced by those families.

What other factors are associated with overweight/obesity at age 10?

As may be expected, a number of lifestyle and dietary factors were found to be associated with overweight/obesity at age 10. Of particular note was mother's BMI. Children whose mother was obese were significantly more likely to be overweight or obese themselves at age 10. This suggests that for these children the family environment – including meals and activities – may be more obesogenic than for children whose mothers are a healthy weight, having a negative effect on the family as a whole. Relatedly, the findings also demonstrated that many parents of overweight and obese children did not accurately perceive their children to be overweight. In such scenarios we may assume that parents will not necessarily be taking steps to address some of the factors which may be maintaining the child's overweight status. Together these findings support the need for family-based interventions to tackle childhood overweight and obesity.

Other factors associated with overweight/obesity were also largely measures of children's experiences and activities at home. Only limited measures of diet were included in the analysis, of these irregular breakfast habits (only occasionally having breakfast) was associated with overweight/obesity. Having less than the recommended amount of sleep was also associated with overweight/obesity though this did not remain significant after controlling for other differences.

Children's sedentary behaviour was also important. Children who were reported as having higher weekly screen time were more likely to be overweight/obese at age 10. And whilst not a direct measure of sedentary time, children with a TV in their bedroom – perhaps facilitating greater opportunity for sedentary behaviour – were more likely to be overweight or obese at age 10 than those without. Both factors remained significant after controlling for other differences between the children.

By far the strongest predictor of overweight/obesity at age 10 was BMI status at age 6. After taking into account social background and other differences, children who were overweight or obese at age 6 were significantly more likely than those of a healthy weight to be overweight or obese at age 10. Echoing the finding already discussed above this further strengthens the rationale for education and intervention during the earliest years of children's lives.

Which factors are associated with a move out of or a move into overweight and obesity between ages 6 and 10?

The longitudinal nature of GUS and the ability to track children's weight change over time provide an opportunity to assess factors associated with a change in BMI between ages 6 and 10. The factors found to be associated with such changes were similar to those associated with overweight/obesity at age 10.

After taking into account social background and other differences between the children, moving into overweight was independently associated with having a mother who was obese and higher weekly screen time. The results also tentatively suggest having a TV in the child's bedroom and irregular breakfast habits may also be linked, though the relationships were not statistically significant. These findings reflect those discussed above, demonstrating some influence from the child's family environment and parental behaviours.

Again, after controlling for differences in other variables, moving out of overweight was associated with lower household income, less frequent consumption of unhealthy snacks and not having a TV in the child's bedroom. Thus a different, but logical, combination of factors suggesting that reducing BMI between ages 6 and 10 was associated with a healthier diet and lower levels of inactivity. The relationship with household income may reflect that a higher proportion of children from lower income households were overweight/obese at age 6 creating more opportunity for children to move out of overweight than amongst children from the highest income group. It nevertheless presents an encouraging message that, whilst inequalities in overweight do increase between ages 6 and 10, positive change can be achieved amongst higher risk groups.

7.2. Concluding remarks

This report has demonstrated a notable increase in rates of overweight and obesity in children between age 6 and age 10. Indeed, BMI increased by an average of 2.5 points for all children over this period. The findings also show that inequalities in levels of overweight/obesity between children from different social backgrounds – which already exist at age 6 – have widened by age 10. This makes subsequently reducing that inequality more difficult as children move into adolescence and through onto adulthood.

A key factor shown to predict overweight and obesity at age 10 was being overweight or obese at age 6. Similarly, the majority of children who were a healthy weight at age 6 were also a healthy weight at age 10. This suggests that addressing factors associated with being overweight in the early years and thus increasing the proportion of younger children of healthy weight would have a knock on effect, reducing levels of overweight in later childhood.

Earlier analysis of GUS data (Parkes et al, 2012) found mother's overweight/obesity, frequency of unhealthy snacks and other indicators of a poorer diet, and low parental supervision to be associated with overweight/obesity at age 6. Many of these aspects of children's family environment and experiences appear to continue to be linked with overweight and obesity as they move through primary school. Notably, though, inactivity – and perhaps particularly a home environment which facilitates higher levels of inactivity - appears to play a more important role when children are slightly older.

Poor parental recognition of child overweight/obesity may also be problematic. The findings suggest that many parents are ill-informed or find overweight hard to recognise, a sensitive issue to address. Thus interventions to reduce child overweight and obesity would likely benefit from the involvement of parents and the wider family along with steps to address issues in the home environment.

It should be noted that the analysis within this report does not demonstrate causal relationships between the factors considered and overweight/obesity. Associations may be due to other confounding factors that have not been studied, including influences that pre-date the birth of the child and inherited effects. Nevertheless, the findings do provide some indication of the key influencing factors amongst children's day-to-day environments and experiences which may be modifiable in order to prevent and tackle increasing levels of overweight and obesity between early and middle childhood.