Obesity

3.4 Obesity



Louise A. Baur



Introduction


Paediatric obesity is a major public health problem in both developed and developing countries. Obese children and adolescents may suffer from a host of co-morbidities, some of which are immediately apparent, whereas others act as warning signs of future disease. Obesity can be a serious, chronic, relapsing disease. It is a disorder of energy imbalance that arises as a consequence of a complex interaction between genetic, social, behavioural and environmental factors. Although investment in primary prevention is vital in curbing the epidemic, effective treatment of those children and adolescents who are currently obese is also needed to improve both their immediate and long-term health outcomes.



image Practical points




• Obesity is a chronic disorder of energy imbalance – focus upon both sides of the energy balance equation: energy in and energy out.


• Measure body mass index (BMI) and plot on a BMI-for-age chart. Measure and record waist circumference, and calculate waist : height ratio.


• In pre-pubertal children, weight maintenance or reduction in the rate of weight gain, may be appropriate goals of therapy. Weight loss is often necessary for moderately obese younger children, and for adolescents.


• For younger children, focus upon the parents as agents of change. Adolescents will require a different, developmentally sensitive, approach.


• Long-term behavioural change is required, involving an increase in incidental physical activity, a reduction in sedentary behaviour and a sustainable change to a lower energy intake.


• There is a role for drug therapy in adolescents who have moderately severe obesity, or those with clinical insulin resistance.


• Prevention of obesity requires a whole-of-system approach in which many aspects of the broader food and physical activity environment are targeted.



How is paediatric overweight and obesity defined?



Body mass index – a measure of total body fatness


Body mass index (BMI; weight/height2; kg/m2) is a simple measure of body fatness. BMI varies dramatically with age and sex during childhood and adolescence: it increases in the first year, falls during preschool years, and then rises once more into adolescence. The point at which BMI starts to increase again, between 4 and 7 years of age, is termed the point of ‘adiposity rebound’ (Figs 3.4.1–3.4.4).


image

Fig. 3.4.1 Body mass index-for-age chart for girls aged 5–19 years.


Source: 2007 World Health Organization Reference. Available at: http://www.who.int/growthref/cht_bmifa_girls_perc_5_19years.pdf


image

Fig. 3.4.2 Body mass index-for-age chart for boys aged 5–19 years.


Source: 2007 World Health Organization Reference. Available at: http://www.who.int/growthref/cht_bmifa_boys_perc_5_19years.pdf


image

Fig. 3.4.3 Body mass index-for-age chart for girls aged 0–5 years.


Source: World Health Organization Child Growth Standards. Available at: http://www.who.int/childgrowth/standards/cht_bfa_girls_p_0_5.pdf


image

Fig. 3.4.4 Body mass index-for-age chart for boys aged 0–5 years.


Source: World Health Organization Child Growth Standards. Available at: http://www.who.int/childgrowth/standards/cht_bfa_boys_p_0_5.pdf


Several countries have their own BMI-for-age growth charts that can be used clinically to chart an individual’s BMI and monitor changes over time. The World Health Organization has also developed BMI-for-age charts for international use for children aged 0–5 and 5–19 years (see Figs 3.4.1–3.4.4). Until further research helps establish the relation between BMI-for-age cut-points and health outcomes in childhood and adolescence, the decision as to which specific centile lines denote overweight and obesity in clinical settings ultimately remains arbitrary.



Waist circumference and waist : height ratio – measures of fat distribution


In children and young people, just as in adults, waist circumference is correlated with abdominal fat, as well as with cardiovascular risk factors. Although waist circumference charts are available for some individual countries, there are no internationally accepted criteria for high- or low-risk waist circumference in this age group. Nationally developed waist circumference-for-age charts can be used to monitor clinical progress of an individual patient.


Waist-to-height ratio (waist/height) is an additional measure of fat distribution that is easy to calculate and reasonably independent of age and sex for individuals aged above 6 years. Waist-to-height ratios greater than 0.5 are associated with increased cardiometabolic risk factors. The clinical message is: ‘Keep your waist to less than half your height’.



Racial and ethnic variations in definition


There are racial and ethnic variations in the biological response to excess adiposity. Among adults, Asians generally have a higher percentage body fat for a given BMI and an associated increased health risk at lower BMI values compared with Europeans, whereas Pacific populations generally have a lower percentage body fat and a decreased health risk at the same BMI levels. These differences are also likely within the child and adolescent age group, and ultimately require the development of ethnic- or race-specific definitions or criteria for obesity.



What is the prevalence of paediatric overweight and obesity?



International prevalence rates and secular trends


Worldwide, approximately 10% of school-aged children and adolescents are overweight, with 2–3% being obese. Prevalence rates vary across regions, with higher rates in children from the Americas, Europe and the Pacific than in those from sub-Saharan Africa or Asia. In 2007 in Australia, approximately 1 in 4 children and adolescents were overweight or obese. In 2006–2007 in New Zealand, 29% of children and adolescents were overweight or obese, with higher rates being found in Pacific and Maori children.


Of most concern are the rapid changes in obesity prevalence in many countries in several continents. Several Asian countries that are experiencing rapid changes in urbanization and nutrition have seen increasing rates of obesity in paediatric populations in recent years. For example, urban Chinese and Vietnamese younger children now have similar obesity rates to those of children in Australia. In addition, overweight children are heavier than in the past. Such findings have very significant implications for future population health strategies.



What are the complications of paediatric obesity?


The complications of obesity among children and adolescents may be immediate or may not manifest until the medium- to long-term. They affect many body systems, as outlined in Table 3.4.1.


Table 3.4.1 Potential obesity-associated complications in children and adolescents

































System Health problems
Psychosocial Social isolation and discrimination, decreased self-esteem, learning difficulties, body image disorder, bulimia
Medium and long term: poorer social and economic ‘success’, bulimia
Respiratory Obstructive sleep apnoea, asthma, poor exercise tolerance
Orthopaedic Back pain, slipped femoral capital epiphyses, tibia vara, ankle sprains, flat feet
Hepatobiliary Non-alcoholic fatty liver disease, gallstones
Reproductive Polycystic ovary syndrome, menstrual abnormalities
Cardiovascular Hypertension, adverse lipid profile (low HDL cholesterol, high triglycerides, high LDL cholesterol)
Medium and long term: increased risk of hypertension and adverse lipid profile in adulthood, increased risk of coronary artery disease in adulthood, left ventricular hypertrophy
Endocrine Hyperinsulinaemia, insulin resistance, impaired glucose tolerance, impaired fasting glucose, type 2 diabetes mellitus
Medium and long term: increased risk of type 2 diabetes mellitus and metabolic syndrome in adulthood
Neurological Benign intracranial hypertension
Skin Acanthosis nigricans, striae, intertrigo

HDL, high-density lipoprotein; LDL, low-density lipoprotein.



Complications during childhood and adolescence



Psychosocial complications


The most common consequences of obesity in childhood and adolescence are those related to psychosocial dysfunction and social isolation. In pre-adolescent children, physical appearance and athletic competence self-esteem are lower than in their normal weight peers, although global self-esteem appears to be preserved. In adolescent girls, excess weight is significantly related to body dissatisfaction, drive for thinness and bulimia. Cross-sectional studies of teenagers show an inverse relationship between weight and both global self-esteem and body-esteem. The pervasive, negative social messages associated with obesity in many communities may have a particular impact during adolescence.


There are differences in health-related quality of life between obese and non-obese children. In randomly sampled populations, the physical and social domains of health-related quality of life for obese children are lower than for non-overweight children. Severely obese patients have significantly reduced health-related quality of life compared with healthy children, having similar quality of life scores to children diagnosed with cancer.



image Clinical example



Trudy, a 13-year-old girl with obesity


Trudy presented to her general practitioner (GP) with a respiratory tract infection. Her mother commented incidentally that Trudy was concerned about her weight and was being teased at school. Indeed, she had left her previous school because of bullying and now it appeared to be starting afresh in the new school.


Trudy is an only child, with a good relationship with her parents and some peers. She is in good general health, apart from the weight gain. Several family members are obese (mother and three grandparents), her paternal grandfather has type 2 diabetes, and her maternal grandfather has hypercholesterolaemia and ischaemic heart disease. Trudy leads a sedentary lifestyle: she enjoys playing music, sewing, reading and talking on the phone. Trudy is driven to and from school each day and watches 3 hours of television per day. Her dietary intake includes skipping breakfast, full-cream milk, ‘something nice’ for morning and afternoon tea, buying food at the milk-bar in the afternoon, a daily intake of 500 mL of soft drink and free access to biscuits at home.


On examination, Trudy’s height was 161.5 cm (< 75th centile), weight 74.3 kg (> 97th centile), BMI 28.4 kg/m2 (> 95th centile for age; adult overweight range), waist circumference 89 cm (adult female ‘at significant risk of metabolic complications’ range) and waist : height ratio 0.55 (> 0.5, indicative of cardiometabolic risk). She was in mid-puberty, and had abdominal and upper thigh striae. Blood pressure was 120/80 mmHg. A fasting blood test showed a normal glucose (4.6 mmol/L; normal range 3.5–5.5), mild hyperinsulinaemia (115 pmol/L) and a lipid profile characteristic of central obesity: total cholesterol 5.3 mmol/L (normal range 2.6–5.5), high-density lipoprotein (HDL) cholesterol 0.8 mmol/L (normal > 0.9), triglycerides 1.9 mmol/L (normal range 0.6–1.7).



Management


The GP arranged to see Trudy and her mother, separately and together, initially every 3 weeks, and then less frequently. Two visits to a local dietitian were also arranged; more frequent follow-up could not be organized. Trudy was encouraged to set her own goals for food and activity changes; these goals were re-visited at the consultations. She was helped to look at ways in which eating cues could be recognized and modified. The family was supported to make changes to their eating patterns and the use of the television in the home.



Progress


In time, Trudy’s mother lost some weight as a result of altered cooking practices and being more active. Water was offered at the evening meal instead of soft drink, less healthy snacks were no longer stored in the cupboards, and the family started eating more vegetables and had smaller meat and rice/potato portions at the evening meal. Trudy ate something for breakfast each morning and started walking to and from school. She started tennis lessons and found an interest in tap dancing.


Ten months later, Trudy’s weight was 69.3 kg, height 163.0 cm, BMI 26.1 kg/m2, waist circumference 81 cm and waist : height ratio 0.50. She reported being fitter and said she was greatly enjoying school and was no longer being bullied. A repeat fasting blood test showed an improved lipid profile (total cholesterol 4.8 mmol/L, HDL cholesterol 1.0 mmol/L, triglycerides 1.4 mmol/L) and a decreased insulin concentration (85 pmol/L), consistent with a reduction in central obesity.



Orthopaedic complications


Slipped capital femoral epiphyses occur much more commonly in obese young people and much earlier than in non-obese patients. Blount disease (tibia vara) is a deformity of the medial portion of the proximal tibial metaphysis that arises as a result of increased weight-bearing on cartilaginous bone with subsequent compensatory overgrowth and bowing of the tibia. Obese young people also have low bone area and bone mass relative to their body weight, making them more prone to fractures than lean individuals.


Minor orthopaedic obesity-associated complications include knock knee (genu valgum), a decreased recovery from soft tissue ankle injuries, and flat, wide feet with increased static and dynamic plantar pressures. These conditions may seem relatively trivial in health terms, but could have a significant impact on a child’s ability to participate fully in activities.



Hepatobiliary complications


Obese children and adolescents may experience a range of gastrointestinal and hepatobiliary disorders, the most significant being non-alcoholic fatty liver disease (NAFLD). NAFLD is an umbrella term that includes steatosis as well as steatohepatitis. It typically presents as an asymptomatic increase in the level of aminotransferases. The degree of steatosis is associated with the severity of obesity, a central fat distribution, hypertriglyceridaemia, insulin resistance and the presence of raised aminotransferases, with an increased level of alanine aminotransferase being most specific for steatosis. Liver fibrosis and even evolving cirrhosis have been identified in liver biopsy findings of paediatric patients with NAFLD.


Several clinical audits from paediatric surgical units have demonstrated an association between cholesterol cholelithiasis and obesity in children and adolescents. Gastro-oesophageal reflux is more prevalent in obese individuals, possibly secondary to increased intra-abdominal pressure.



Neurological complications


Idiopathic raised intracranial pressure (pseudotumour cerebri) is a rare but potentially very serious complication of obesity. The role played by obesity in the pathogenesis of the disorder is unknown.



Asthma and sleep-disordered breathing


Respiratory outcomes can be poor in obese children. Asthma is more prevalent in obese than non-obese children. Compared with lean children with asthma, overweight and obese children use more antiasthma medications, have more wheezing episodes and experience more unscheduled visits to hospital. Obese children also have a lower exercise tolerance than their lean peers, presumably compounding their obesity.


Potentially more serious is the complication of obstructive sleep apnoea. Between 1 in 10 and 1 in 4 obese children have obstructive sleep apnoea. Obstructive sleep apnoea is associated with severity of obesity, insulin resistance and dyslipidaemia. Profound hypoventilation and even sudden death have been reported in severe cases of obesity-associated sleep apnoea.



Risk factors for cardiovascular disease


Risk factors for cardiovascular disease are one of the most common problems facing the obese young person. In the famed Bogalusa Heart Study from the USA, 60% of overweight 5–10-year-olds had one cardiovascular risk factor, such as hypertension, high low-density lipoprotein (LDL) cholesterol or high triglycerides, and over 20% had two or more risk factors. Overall, when compared with their lean peers, overweight children were 2.4 times as likely to have raised total cholesterol and diastolic blood pressure, and 4.5 times as likely to have increased systolic blood pressure. A central fat distribution is particularly associated with clustering of cardiovascular risk factors.



Endocrine complications


Overweight children are much more likely to have raised fasting insulin concentrations (indicative of insulin resistance), impaired fasting glucose or glucose intolerance than their lean peers. Although still rare among children and adolescents, the incidence of type 2 diabetes mellitus is increasing and is inextricably linked to the prevalence of obesity among young people. Type 2 diabetes is more common in adolescents and those who are obese, have acanthosis nigricans (thickened pigmented skin at the base of the neck and in flexures, characteristic of insulin resistance; Fig. 3.4.5), have a family history of type 2 diabetes or are female.


image

Fig. 3.4.5 Acanthosis nigricans, seen at the base of the neck of an adolescent male with obesity and hyperinsulinaemia.

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Aug 4, 2016 | Posted by in PEDIATRICS | Comments Off on Obesity

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