Milligan, F. (2008) Child obesity 1: exploring its prevalence and causes. Nursing Times; 104: 32, 26–27.
This is a two-part unit on childhood obesity, which is a major public health concern. With rising levels of the condition it is increasingly obvious that early intervention is key to halting this trend. This first part outlines the prevalence and definition of obesity, and also explores its causes and possible interventions.
Fiona Milligan, PGDip Public Health, BSc, Dip Counselling, Dip Health Promotion, RGN, is clinical nurse specialist in cardiac rehabilitation and clinical lead in non-medical prescribing, Chelsea and Westminster Hospital NHS Foundation Trust, London.
- Know the definition of obesity in both adults and children.
- Understand the causes and contributory factors in obesity.
Obesity can lead to several diseases that impact negatively on quality of life, morbidity and mortality outcomes in large population groups. A number of measures have been introduced in the UK to address this, involving a combination of behavioural change strategies. However, there remains a lack of empirical evidence from trial data on the effectiveness of planned interventions, and this should be addressed through improved methodological study design. A comprehensive strategy by multi-sector agencies is needed to deliver appropriate and timely interventions.
Prevalence of obesity
The prevalence of children who are overweight or obese has increased substantially since 1984. It is becoming one of the most common childhood health problems in Europe and has the greatest impact for future negative health consequences (Chinn and Rona, 2001).
Obesity increases the risk of several health problems such as cardiovascular disease and diabetes. It also contributes to social isolation as a result of psychological distress, low self-esteem and practical difficulties (World Health Organization, 2004).
The International Obesity Taskforce (IOTF, 2001) identified that in the UK almost two million children were overweight and 700,000 were classified as obese. The Health Survey for England (Sproston and Primatesta, 2003) found 21.8% of boys and 27.5% of girls aged 2–15 years were overweight or obese. It found the prevalence of obesity almost doubled among boys (from 2.9% to 5.7%) and increased by over half among girls (from 4.9% to 7.8%), between 1995–2002. The British Heart Foundation (2006) found that in boys aged 2–15 years, 16% were identified as overweight with 6% classed as obese. In girls in the same age range, 20% were overweight and 7% obese. In England alone it is predicted that by 2020 one-fifth of boys and one-third of girls will be classified as obese (Department of Health, 2004).
Evidence suggests a global epidemic of obesity. Statistics from a WHO (2004) report on global trends showed England had the steepest increase in the prevalence of overweight children from 1960–2000.
These findings were underpinned by data from Sproston and Primatesta’s (2003) health survey, which revealed an alarming increase in the incidence of overweight and obesity in children in England. The report also identified a linear relationship between social class and prevalence of overweight or obesity, in that prevalence was higher in more deprived groups.
Definition of obesity
Obesity is defined as an excess of body fat as measured by body mass index (BMI) ratio in adults – this is calculated by dividing weight in kilograms by height in metres squared. In adults, a BMI over 25 is classified as overweight and over 30 as obese (classes I, II or III or moderate, severe or morbidly obese) (WHO, 2004).
To ensure a standardisation of measurement and allow for comparative analysis in children, the IOTF compiled data from surveys in six countries on health and nutrition. This was used to compose growth curves which relate to standardised cut-off points for different age groups and sex corresponding to adult BMI measurements (IOTF, 2001)The sensitivity and specificity of the IOTF classification for children was found to be less sensitive in the higher obesity cut-off point but had excellent sensitivity and specificity in the cut-off point for overweight (Reilly et al, 2000)
The importance of age and sex-specific growth curve cut-off points corresponding to BMI values is that it allows tracking of obesity in childhood through adolescence to adulthood. A number of studies have identified that childhood obesity has a high risk of persistence into adulthood. It is estimated obese children have a 25–50% chance of progression to adult obesity, with adolescents having a 78% risk (New South Wales Childhood Obesity Secretariat, 2002).
This would underpin current strategies involving behavioural change models targeting young children. There have been suggestions that preschool age (from three years onwards) is the time to address the issue (Rudolf et al, 2001).
Causes of obesity
To implement appropriate and effective public health interventions to reduce the growing incidence of obesity in children and adolescents, the WHO (2004) examined causative or contributing factors on an international scale. It was suggested the cultural environment in some countries endorses the ethos of sedentary behaviour and larger physical appearances. These characteristics are perceived to signify health and status. Changing social patterns and urbanisation were also implicated as global factors impacting negatively on health (WHO, 2004).
It is interesting to note that data from a UK population survey lends weight to the theory of social and cultural behaviours as causative factors in lifestyle choices (Sproston and Primatesta, 2003). Prevalence of overweight and obesity was higher in lower socio-economic groups, which correlates with a substantial body of empirical evidence showing that unhealthy lifestyle behaviours are common features of lower socio-economic households or areas of social deprivation (Acheson, 1998).
Some debate remains about the origin of these inequalities and whether they are structural and material or cultural and behavioural. In the case of structural and material inequalities, it could be argued that making healthy food more affordable and implementing sustainable social policies to regenerate deprived communities would be the most effective intervention. However, inherited behaviours also feature highly – obese children often have one or more parent classified as obese.
Among the general population, activity levels and the proportion of the population meeting recommended levels increased between 1999 and 2004. However, there was little change in black and minority ethnic (BME) groups, apart from in Chinese men and Indian women. On the other hand, intake of low-fat foods and recommended amounts of fruit and vegetable consumption were high in BME groups compared with the general population. These adult behavioural trends tended to be echoed in the lifestyle behaviours of children within particular BME groups (Sproston and Mindell, 2006). This would suggest changing the environment in which people live may not necessarily change their behaviours.
Strategies need to focus on a combination of behavioural change interventions within social and family groups at local level and environmental change at national level (DH, 2004b). A report from the government’s futures think tank (Foresight, 2007) found that preventing obesity requires major, multidimensional change – in the environment, behaviour, organisations, communities, families and individuals.
Of course, rising levels of overweight and obesity may simply be the result of over-eating and inactivity. An imbalance between calorie consumption and energy expenditure in children and young adults is thought to be the main cause of the problem.
The Food Standards Agency (2000) identified basic dietary deficiencies in fruit and vegetable consumption, while a substantial proportion of UK children were exceeding adult recommendations for the intake of foods high in saturated fat, salt and sugar. In addition, activity levels in 30% of boys and 40% of girls do not meet recommendations (a minimum of one hour a day).
The estimated cost of obesity in the UK is approximately £3.7bn per year, while the combined cost of obesity and overweight is estimated to be around £7.4bn (House of Commons Health Committee, 2004).
A projection of the total costs of treating obesity and its consequences ranges from 2–6% of total healthcare expenditure (DH, 2006). However, ultimately this is a preventable expenditure.
Obesity exists mainly as a consequence of the actions of individuals. Genetic and metabolic factors are contributory factors. Governments have also been slow to reduce health inequalities and implement urban regeneration. Effective behavioural change interventions and improved social policy would appear to be the most cost-effective and sustainable action plan in the long term.
A better understanding of why individuals participate in particular behaviours may also improve outcomes in strategies to reduce obesity levels. The government has allocated a fairly substantial sum to combat the growing prevalence of obesity, with £1bn allocated to nutrition and activity interventions and a further £3.6bn devoted to combined family and school programmes which may impact positively on behavioural change (National Audit Office, 2006). These strategies appear to provide a multi-faceted approach to this complex issue.
A crucial element of determining effectiveness of interventions will be the evaluation of robust and standardised data collected on identifiable outcome measures. An economic assessment of research on the impact of interventions will form the core of evidence to support effectiveness of multi-sector involvement (NAO, 2006).
The Foresight (2007) report concluded that only a comprehensive long-term strategy would reduce rising levels of obesity.
Department of Health (2004a) Summary of Intelligence on Obesity.
Foresight (2007) Tackling Obesities: Future Choices – Project Report.
Sproston, K., Mindell, J. (2006) Health Survey for England 2004. Volume 1: The Health of Minority Ethnic Groups
Sproston, K., Primatesta, P. (2003) Health Survey for England 2002: The Health of Children and Young People.
World Health Organization (2004) A Global Strategy on Diet, Physical Activity and Health.