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Discuss the current prevalence of obesity among children in the UK and outline why rates of obesity in this population group may be rising.
Introduction
At a simplistic level, the casual observer may be forgiven for thinking that it is a comparatively easy task to ascertain the number of obese children in the UK. Sadly, as this essay will demonstrate, it is neither easy nor straightforward, as there are many confounding factors that contribute to a definition of obesity.
It is clearly important, when considering a subject such as this, to define an evidence base. (Sackett, 1996). It is this definition that is likely to prove one of the problems that we must negotiate in order to arrive at a meaningful discussion.
A brief examination of the literature on the subject shows us that there are a number of perfectly rational indices of body size that can (and are) used to determine the size of a child. Skin fold thickness, abdominal girth and BMI to name but three. These indices are frequently seen in academic papers and are often cited in evidence for obesity. In order to make a rational examination of the situation, one must consider the relationship between each of these factors and how they correlate with any rational definition of obesity. (Neovis M et al 2004)
Measuring obesity
Measuring obesity in the adult is a much less contentious issue, as there appears to be general acceptance that the BMI is a workable standard for an assessment of over- and underweight individuals. (REC 1995). It appears that it provides a sensitive and workable tool which correlates well with indices that measure all cause mortality and morbidity. (Calle E et al 1999)
To this extent, the BMI has been categorised into six divisions: one underweight, one normal and four described as indicating varying degrees of obesity. (IOTF 1998). There appears to be a general consensus that the BMI correlates better with the other predictive health indices than other indices such as the already mentioned skinfold measurement, the kg/m and kg/m3 indices. (Rolland-Cachera MF et al. 1989)
Many published studies have, for this reason, utilised the BMI as a suitable tool for the assessment of body size in the child with reference charts being drawn up and widely utilised as reference guides.(Cole TJ et al 1990).
The reason for this rather detailed consideration is that the realisation that the BMI, as an assessment of body size, is also dependent on both age and pubertal status. These factors are clearly not a major consideration in the adult, but take on a much greater potentially confounding significance when one is considering the status of the child.
Consideration of this issue has allowed certain authorities such as the WHO to suggest that the best expression of the BMI for children is as in relation to the standard deviations from the mean (SDS – Standard deviation scores) for each age band. (Dietz WH et al 1998). The authors also point out that because there is a general trend for the population in the UK (and elsewhere) to become taller, even this reference point is relative and not absolute and is a reflection of the fact that even these values will have to be periodically reviewed and updated. (Fredricks AM et al 2000)
For all of these reasons, one of the most authoritative bodies considering the issue, the European childhood obesity group, has recommended that the paediatric centiles (a reflection of the SDS score), which are identified by a BMI of 20,25 and 30 in children and young adults, should be the generally accepted parameters for identification of underweight, normality, overweight, and extreme overweight. (Dietz WH et al 1998)
Factors that suggest that the prevalence of obesity is increasing
Despite all of our discussion so far, it is still not totally clear cut that the measurement of obesity is a simple parameter that is either going up or down on a National level. If we consider studies such as the Dutch Roede study (et al 1985), which was a meticulous consideration of the size of children in the period 1965-1980. If we examine this study in detail, we can see that there is a demonstrable increase in weight for height (which has actually accelerated after 1980 as other studies have shown that the number of children who have exceeded the 1980 90th centile of BMI has doubled between 1980 and 1997 {Fredriks AM et al. 2002})
In this particular study, the biggest spread of results (and therefore the least discriminatory age band) was seen at the age of six. Over the time scale covered by these two studies, the overall weight distribution has progressively moved upwards in relation to age. Over the same time scale there has also been a significant upwards trend in height for age. (Kotani K et al 1999)
The difficulty that this poses is that overweight and obese children tend to be taller, have more advanced bone age, have earlier puberty and to mature earlier than non-overweight children. This makes the assessment of obesity more difficult, as the height gain is dependent on, and follows shortly after, excessive weight gain. (Luepker RV et al 1997)
Despite these complexities, centile charts were constructed on the figures from the Dietz study. They found that the BMI centiles rose steadily during infancy, they fell during the pre-school period and then rose from 6 yrs. onwards.
The authors were able to conclude from the data, that the age at which the adiposity rebound occurs is highly indicative of the incidence of obesity in adult life. The best evidence therefore that the trend towards obesity in adult life is increasing is that the typical age of the adipose rebound in the Dietz study was 6 yrs. and in the subsequent Fredriks study, it had dropped to 5.5 yrs. From other work (Must A et al 1999) we can conclude that the earlier the age of the rebound, the greater the risk of adult obesity.
This statement is further complicated by the realisation that the lower centiles tend to rebound significantly later than the higher ones (by as much as three years). This is not an isolated phenomenon as it is a common finding in other multinational studies.
We believe that weight is determined by an incompletely understood and certainly complex interaction, between cultural, genetic, socio-economic, environmental and psychosocial factors. All have an independent and interrelated effect on the physiological mechanisms that regulate energy intake and expenditure. We can conclude, with a fair degree of confidence, that the current rise in obesity levels is as a result of the environmental component of these factors, simply because we do not believe that genetic factors could change at such a rapid rate. (Fruhbeck G 2000)
Further evidence of the rise in obesity levels in children came from another large and meticulous UK based study. (Bundred P et al 2001). Over 60,000 children were included in the data base for this study which ran over a ten year period. The authors were able to determine a “highly significant trend” in the increase in the proportion of overweight children.
Those in the overweight category increased from 14.7% to 23.6% of the cohort and those in the obese category increased from 5.4% to 9.2%. Based on this exemplary evidence, there seems no doubt that the prevalence of obesity is increasing.
What are the factors that may be driving this increase?
This is a far more difficult question to answer. We have already discussed the multifactorial dimensions of this problem. There clearly is not one discrete all-encompassing answer. An intuitive suggestion might be that obesity may be linked to an increase in sedentary lifestyles or perhaps a reduction in the levels of physical activity. If one examines the peer reviewed literature on the subject, there is virtually nothing to support this contention and there is also a considerable wealth of evidence to refute it. (Andersem RE et al 1998).
Some studies (Gortmaker SL et al 1996) found no relationship between the amount of physical activity expended and the incidence of obesity in children. This particular study did however, find a statistically significant relationship between obesity and watching television. It is fair to comment that this is a rather contentious finding as other studies have found no relationship between TV viewing and obesity. (DuRant RH et al 1999)
Other authorities (Brugman E et al 1995), have commented that it is not clear that, if there is a correlation, whether it is cause or effect. The obese child may not feel motivated to take physical exercise and may have an increased dietary intake solely by virtue of the fact that they are either watching the TV, or even as a response to the food advertising on the TV.
Why is increasing obesity a problem?
This discussion has been primarily aimed at the issues of whether there is a rising trend in obesity in children. From the evidence presented, there is little doubt that there is a positive trend and also that the incidence of obesity in children is increasing. The question that arises from this finding is clearly, what is the actual significance of this fact? Does it actually matter if the population is getting fatter or taller? (Reilly, JJ. 2002)
In terms of both morbidity and mortality, the answer is an unequivocal “yes”. We shall present and discuss the evidence base for this statement in due course.
The first, and probably the most significant association with childhood obesity, is adult obesity. There are a number of studies that conclusively prove that, to be an obese child is a strong independent risk factor in adult obesity. (Kotani K et al 1999). Bellizzi MC (et al 1999) quantify that risk as between 45-64% (depending on which band of obesity you take as a marker). We have already quoted the Calle trial (1999) which quantified the increased risk of death in overweight adults and found an almost linear relationship between increasing BMI and increasing body weight (beyond the mean). Of all causes of death, cardiovascular disease was the greatest cause with an increase in both atherosclerosis and arteriosclerosis cited as being the most important aetiological factors.
The Berenson study ( et al 1998) quantifies this further with a study into the condition of atherosclerosis in children and young adults and concluded that increased BMI is the strongest independent risk factor in the development of atherosclerotic lesions in the age range of 2-39 yrs.
We should also note that the increase in cardiovascular mortality is also directly related to the increased incidence of the condition of Type II diabetes mellitus which, in itself, is also associated with obesity and abnormalities of both carbohydrate, fat and triglyceride metabolism in the adult. (Stratton I et al 2000)
It follows from this that there is a distinct and pressing need for measures to control this “epidemic of obesity”. (Must A et al.1999)
This is where the whole issue starts to become contentious. We believe that, in this essay, we have produced a strong and robust evidence base to support the arguments that obesity is increasing and that this has a direct and negative effect on the Public Health, both in terms of morbidity and mortality. Clearly each individual has a responsibility to their own determination of their health issues. This comes under the all embracing heading of empowerment and education. It seems entirely appropriate to provide a person with information and assistance to act on that information if required. One could take the view that if an obese person was aware of the risks and chose not to take appropriate action to avoid them, then that would be a matter for themselves alone.
The counter argument is that the increased morbidity and mortality has a knock on effect in terms of cost to the public in general both directly, in terms of increased health related costs, but in ways that are more difficult to quantify such as time lost at work, insurance costs and the cost of a premature death.
There are many studies that attempt to quantify this figure. It is not particularly instructive to examine them as the estimates differ wildly depending upon the extent of each consideration. Suffice it to say that the cost is generally agreed to be colossal.
Citing this as implied justification the Government has produced a number of White Papers and consultation documents, most notably “Saving lives – our Healthier Nation” (1999) and Choosing Health: making healthier choices easier (2004) which are primarily aimed at introducing standards and measures that will attempt to reduce the upward trend of obesity in this country.
With specific regard to the essay topic of childhood obesity we should also consider the National Healthy School Standard (NHSS) is such an important initiative. It was outlined by the Government as a consultation document in the latter part of 1999 as part of the Government’s initiative to improve the health of the Nation. It’s central stated aim was, amongst other things, to have all local authorities working with the scheme by 2002 and all schools adopting the initiatives by 2004.
This was augmented by School Meals – raising the Standard (2005) which was published earlier on this year. All of these measures are, in one way or another, funded by central government, either directly, via the dept. of education or through the NHS.
As a conclusion we feel confident in stating that the phenomenon of childhood obesity is a real and quantifiable one, it is undoubtedly increasing. Its has a deep significance with regard to the problem of adult obesity which, in itself has dire implications for both morbidity and mortality of the population.
Early intervention with empowerment and education, in terms of increasing activity, and an overall reduction in high calorie and high fat foods is clearly important as some workers have been able to demonstrate clear effects from these measures. (Barlow S et al 1998). Other authorities suggest that the particular age range of 0-4 yrs. are particularly cost effective to target. (Bundred P et al 2001)
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