Obesity in children

Abstract

Introduction

Obesity is the result of long-term energy imbalances, where daily energy intake exceeds daily energy expenditure. Along with long-term health problems, obesity in children may also be associated with psychosocial problems, including social marginalisation, low self-esteem, and impaired quality of life. Most obese adolescents stay obese as adults. Obesity is increasing among children and adolescents, with 16.8% of boys and 15.2% of girls in the UK aged 2 to 15 years obese in 2008.

Methods and outcomes

We conducted a systematic review and aimed to answer the following clinical questions: What are the effects of lifestyle interventions for the treatment of childhood obesity? What are the effects of surgical interventions for the treatment of childhood obesity? We searched: Medline, Embase, The Cochrane Library, and other important databases up to January 2010 (Clinical Evidence reviews are updated periodically, please check our website for the most up-to-date version of this review). We included harms alerts from relevant organisations such as the US Food and Drug Administration (FDA) and the UK Medicines and Healthcare products Regulatory Agency (MHRA).

Results

We found 14 systematic reviews and RCTs that met our inclusion criteria. We performed a GRADE evaluation of the quality of evidence for interventions.

Conclusions

In this systematic review we present information relating to the effectiveness and safety of the following lifestyle interventions: behavioural, diet, and multifactorial interventions; physical activity; and bariatric surgery.

Key Points

Obesity is the result of long-term energy imbalances, where daily energy intake exceeds daily energy expenditure.

• Obesity in children is associated with physical as well as psychosocial problems. Long-term adverse health consequences of childhood obesity may include increased risk for cardiovascular and metabolic disease in adulthood.

• Most obese adolescents stay obese as adults.

Obesity is increasing among children and adolescents, with 16.8% of boys and 15.2% of girls in the UK aged 2 to 15 years being obese in 2008.

We don't know how lifestyle or surgical interventions help in improving quality of life of overweight and obese children or in reducing premature deaths associated with childhood overweight and obesity in the longer term.

Multifactorial interventions (behavioural, dietary, and physical) may help overweight and obese children to lose weight.

• Multifactorial interventions may be more effective if they involve the family, are delivered in specialist settings, and combine changes in lifestyle habits, particularly diet and physical activity (generally involving behavioural management techniques).

We don't know if behavioural, dietary, or physical interventions alone can help overweight and obese children lose weight.

We don't know how effective surgical interventions are in treating obesity in children, as we found no high-quality RCTs.

About this condition

Definition

Obesity is a chronic condition characterised by an excess of body fat. It is most often defined by the body mass index (BMI), which is highly correlated with body fat. BMI is weight in kilograms divided by height in metres squared (kg/m²). In children and adolescents, BMI varies with age and sex. It typically rises during the first months after birth, falls after the first year, and rises again around the sixth year of life. Thus, a given BMI value is usually compared against reference charts to obtain a ranking of BMI percentile for age and sex. The BMI percentile indicates the relative position of the child's BMI as compared with a historical reference population of children of the same age and sex. Worldwide, there is little agreement on the definition of overweight and obesity among children; however, a BMI above the 85th percentile is generally considered to be at least "at risk for overweight" in the USA and UK. A BMI above the 95th percentile is variably defined as overweight or obese but generally indicates a need for intervention. In this review, we have considered treatment of children for overweight and obesity, including children with a BMI above the 85th percentile for age and sex in a community setting. We have included interventions given to the children, their parents, or both.

Incidence/ Prevalence

The prevalence of obesity (generally BMI >95th percentile) is steadily increasing among children and adolescents. In the UK in 2008, it was estimated that 16.8% of boys and 15.2% of girls aged 2 to 15 years were obese, which was an increase from 11.1% in boys and 12.2% in girls in 1995, but a decrease from 19.4% in boys and 18.5% in girls in 2004.

Aetiology/ Risk factors

Obesity is the result of long-term energy imbalances, where daily energy intake exceeds daily energy expenditure. Energy balance is modulated by a myriad of factors, including metabolic rate, appetite, diet, and physical activity. Although these factors are influenced by genetic traits in some children, the increase in obesity prevalence in the past few decades cannot be explained by changes in the human gene pool, and is more often attributed to environmental changes that promote excessive food intake and discourage physical activity. The risk of childhood obesity is related to childhood diet and sedentary time. Other risk factors are parental obesity, low parental education, social deprivation, infant feeding patterns, early or more rapid puberty (both a risk factor and an effect of obesity), extreme (both high and low) birth weights, and gestational diabetes. Specifically, physical activity levels have decreased over the years and now only 36% of children and adolescents in the USA are meeting recommended levels of physical activity. Among British children aged 4 to 15 years whose physical activity levels were objectively assessed using accelerometry, only 33% of boys and 21% of girls met the government recommendation for daily physical activity level. Less commonly, obesity may also be induced by drugs (e.g., high-dose glucocorticoids), neuroendocrine disorders (e.g., Cushing's syndrome), or inherited disorders (e.g., Down's syndrome and Prader–Willi syndrome).

Prognosis

Most obese adolescents will become obese adults. For example, a 5-year longitudinal study of obese adolescents aged 13 to 19 years found that 86% remained obese as young adults. Obesity is associated with a higher prevalence of insulin resistance, elevated blood lipids, increased blood pressure, and impaired glucose tolerance, which in turn may increase the risk of several chronic diseases in adulthood, including hypertension, dyslipidaemia, diabetes, cardiovascular disease, sleep apnoea, osteoarthritis, and some cancers. Perhaps a less recognised but important short-term comorbidity of overweight/obesity, particularly in adolescent children, is functional impairment in several psychosocial domains, including social marginalisation, low self-esteem, and impaired quality of life. It is important that clinicians emphasise improvements in diet, physical activity, and health independently of changes in body weight.

Aims of intervention

To achieve gradual reduction in BMI and BMI percentile, and to prevent the morbidity and mortality associated with obesity, without undue adverse effects. In children, a reduction in BMI can often be achieved by maintaining current body weight during normal growth in height with ageing.

Outcomes

Change in overweight Proxy measures assessed in studies included mean weight loss (kg), change in BMI (kg/m²), change in BMI z score, change in BMI percentile, change in percentage overweight or obese (percent over the median weight for age and sex), and change in other adiposity indicators (waist circumference, hip circumference, waist-hip ratio, total fat mass, percentage fat mass). Mortality (associated with obesity). Quality of life. Adverse effects.

Methods

Clinical Evidence search and appraisal January 2010. The following databases were used to identify studies for this systematic review: Medline 1966 to January 2010, Embase 1980 to January 2010, and The Cochrane Database of Systematic Reviews 2009, Issue 4 (1966 to date of issue). An additional search within The Cochrane Library was carried out for the Database of Abstracts of Reviews of Effects (DARE) and Health Technology Assessment (HTA). We also searched for retractions of studies included in the review. Abstracts of the studies retrieved from the initial search were assessed by an information specialist. Selected studies were then sent to the contributor for additional assessment, using predetermined criteria to identify relevant studies. Study design criteria for inclusion in this review were: published systematic reviews of RCTs and RCTs in any language; RCTs could be open or blinded, containing 20 or more individuals per arm, of whom 80% or more were followed up. Minimum length of follow-up was 12 weeks. We included studies in overweight and obese children (aged 18 years and younger), including children with a BMI above the 85th percentile for age and sex. We included systematic reviews of RCTs and RCTs where harms of an included intervention were studied applying the same study design criteria for inclusion as we did for benefits. In addition we use a regular surveillance protocol to capture harms alerts from organisations such as the FDA and the MHRA, which are added to the reviews as required. We categorised studies of lifestyle interventions into 4 broad (and non-mutually exclusive) groups on the basis of the type of intervention given. We applied the following principles and definitions to do this. Multifactorial interventions involve the use of more than one mode of intervention (behavioural, diet, physical activity, or a combination) to reduce obesity or overweight. Behavioural interventions involve behavioural/cognitive theories or behavioural management principles to change behaviours that contribute to obesity. Where these theories were not described explicitly, we considered interventions to be behavioural if the mode of delivery involved behavioural techniques. However, most of the studies examining behavioural interventions tended to be classified as multifactorial interventions because these interventions aimed to exert their effects by modifying diet, level of physical activity, or both and so we could not separate the effect of the behavioural intervention from the effect of dietary and activity changes. So, in these cases, we have included these studies in the multifactorial option. We considered studies under the behavioural intervention option only if the study design enabled us to compare different behavioural intervention techniques or to separate the effects of the behavioural intervention from the effects of diet, exercise, or both. Examples are where the study allowed comparison of various intensity/types/modes/methods of specific behavioural interventions. Studies comparing dietary interventions involve comparing the effect of different diets (type or quantity of diet or delivery of dietary intervention) while holding other factors comparable between treatment groups. Studies comparing physical activity interventions involve the comparison of the effect of physical activity (mode or quantity) or any of its indicators (television watching, frequency and/or duration of exercise, etc). To aid readability of the numerical data in our reviews, we round many percentages to the nearest whole number. Readers should be aware of this when relating percentages to summary statistics such as relative risks (RRs) and odds ratios (ORs). We have performed a GRADE evaluation of the quality of evidence for interventions included in this review (see table). The categorisation of the quality of the evidence (high, moderate, low, or very low) reflects the quality of evidence available for our chosen outcomes in our defined populations of interest. These categorisations are not necessarily a reflection of the overall methodological quality of any individual study, because the Clinical Evidence population and outcome of choice may represent only a small subset of the total outcomes reported, and population included, in any individual trial. For further details of how we perform the GRADE evaluation and the scoring system we use, please see our website (www.clinicalevidence.com).

Table.

GRADE Evaluation of interventions for Obesity in children.

Important outcomes	Change in overweight, Mortality, Quality of life
Studies (Participants)	Outcome	Comparison	Type of evidence	Quality	Consistency	Directness	Effect size	GRADE	Comment
What are the effects of lifestyle interventions for the treatment of childhood obesity?
at least 20 (at least 1223)	Change in overweight	Multifactorial interventions versus no treatment/usual care	4	–1	0	–2	0	Very low	Quality point deducted for statistical heterogeneity in analysis. Directness points deducted for diverse interventions and comparisons
8 (455)	Change in overweight	Dietary interventions alone versus usual care/no treatment	4	0	0	–2	0	Low	Directness points deducted for diverse interventions and comparisons
at least 17 (at least 979)	Change in overweight	Physical activity versus no treatment/usual care	4	0	0	–2	0	Low	Directness points deducted for diverse interventions and comparisons

We initially allocate 4 points to evidence from RCTs, and 2 points to evidence from observational studies. To attain the final GRADE score for a given comparison, points are deducted or added from this initial score based on preset criteria relating to the categories of quality, directness, consistency, and effect size. Quality: based on issues affecting methodological rigour (e.g., incomplete reporting of results, quasi-randomisation, sparse data [<200 people in the analysis]). Consistency: based on similarity of results across studies. Directness: based on generalisability of population or outcomes. Effect size: based on magnitude of effect as measured by statistics such as relative risk, odds ratio, or hazard ratio.

Glossary

Behavioural interventions

Strategies to help people acquire the skills, motivations, and support to change diet and exercise patterns.

Low-quality evidence

Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate.

Very low-quality evidence

Any estimate of effect is very uncertain.

Z score

The z score reveals how many units of the standard deviation a case is above or below the mean.

Disclaimer

The information contained in this publication is intended for medical professionals. Categories presented in Clinical Evidence indicate a judgement about the strength of the evidence available to our contributors prior to publication and the relevant importance of benefit and harms. We rely on our contributors to confirm the accuracy of the information presented and to adhere to describe accepted practices. Readers should be aware that professionals in the field may have different opinions. Because of this and regular advances in medical research we strongly recommend that readers' independently verify specified treatments and drugs including manufacturers' guidance. Also, the categories do not indicate whether a particular treatment is generally appropriate or whether it is suitable for a particular individual. Ultimately it is the readers' responsibility to make their own professional judgements, so to appropriately advise and treat their patients.To the fullest extent permitted by law, BMJ Publishing Group Limited and its editors are not responsible for any losses, injury or damage caused to any person or property (including under contract, by negligence, products liability or otherwise) whether they be direct or indirect, special, incidental or consequential, resulting from the application of the information in this publication.