AN OVERWEIGHT BOY

Marlon’s BMI weight (kg)/height (m)2 38.7/(1.25)2 24.8 kg/m2 . There are standard BMI charts for males and females from 0 to 20 years. BMI varies according to age. Children with a BMI above the 91st centile are overweight and those with a BMI above the 98th centile are obese. The most likely cause of this child’s obesity is simple obesity – obesity due to caloric intake exceeding energy expenditure. It is the commonest cause of obesity and is not due to any underlying pathology. Children with simple obesity tend to be tall and overweight. Those who are short and overweight are more likely to have underlying pathology, such as an endocrine disorder. Stretch marks are secondary to the obesity and are usually pink. Violaceous stretch marks are associated with Cushing’s syndrome. Large tonsils and obstructive sleep apnoea are associated with obesity. The child does not have acanthosis nigricans, which is a thickening and darkening of the skin in the axilla, neck or groin. It is usually a sign of insulin resistance. Children with obesity should be assessed for co-morbidities such as hypertension, breathlessness on exertion, obstructive sleep apnoea, hyperinsulinaemia and type 2 diabetes (in children 10 years), dyslipidaemia, knock-knees or bow legs, polycystic ovary syndrome and psychosocial dysfunction.

Causes of obesity

• Simple obesity

• Genetic, i.e. one or both parents is obese

• Endocrine disease, e.g. hypothyroidism, Cushing’s syndrome, growth hormone deficiency, pseudohypoparathyroidism

• Drugs, e.g. steroids, sodium valproate

• Syndromes, e.g. Down’s, Präder–Willi and Laurence–Moon–Biedl • Disorders associated with immobility, e.g. cerebral palsy

• Hypothalamic damage, e.g. secondary to trauma or brain tumours

• Rarely, single gene mutations, such as those of the melanocortin-4 receptor and leptin

Treatment should be multidisciplinary. Dietetic input is very important. Children should be encouraged to exercise for 60 min/day. Sedentary activities such as playing computer games should be discouraged. Obesity can lead to low self-esteem and, in our case, Marlon is being bullied. He would therefore benefit from seeing a psychologist, who could also initiate behavioural therapies to help treat the obesity. As the enlarged tonsils are not leading to sleep apnoea, tonsillectomy is not currently indicated. The systolic blood pressure is below the 95th centile for a 7-year-old male with a height on the 75th centile and therefore does not need treatment. Drug treatment with drugs such as Orlistat or sibutramine is reserved for children 12 years of age and is only recommended in the presence of severe physical or psychological co-morbidities. Post-puberty, bariatric surgery, such as gastric stapling, can be considered in severe cases.

 KEY POINTS

• Body mass index is calculated by weight (kg)/height (m)2.

• A child with a BMI above the 91st centile is overweight and one with a BMI above the 98th centile is obese.

• The commonest cause of obesity is simple obesity.