Published on 21/03/2015 by admin
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Chapter 34 OBESITY
Jonathan M. Wong
Pediatric obesity is defined as a weight that is 20% or more above the mean weight for children of the same height. Severe obesity is defined as a weight that is 40% above the mean weight for children of the same height. Alternatively, a weight greater than the 85th percentile or the 95th percentile may be used to define obesity and severe obesity, respectively. However, this latter definition does not differentiate lean body mass from fat.
The prevalence of childhood obesity has risen significantly in the United States over the past several decades. According to the National Health Examination Survey Cycles, the prevalence of pediatric obesity is estimated to be 25% to 30%. This represents an increase of 54% in children aged 6 to 11 and 39% in adolescents 12 to 17 years old. From 1976 to 2000, the prevalence of severe obesity increased even more, with Hispanic, Native American, and black patients preferentially affected.
The persistence of obesity into adulthood depends on several factors, including the age at which the child becomes obese, the severity of the obesity, and the prevalence of obesity in at least one parent. A child with one obese parent is three times more likely to become obese, whereas a child with two obese parents is 10 times more likely to become obese. Interestingly, children younger than 3 years who are overweight do not have a higher incidence of future obesity unless one parent is obese. After age 3, the likelihood that obesity will persist into adulthood increases with advancing age of the child (50% in a child age 6, and 70% to 80% in adolescents).
Several studies suggest that obese children, on average, do not consume significantly more calories than their nonobese peers. However, a modest increase in calories consumed over time equates to the increase in weight seen in these patients. An increase of 50 to 100 calories per day can result in a 5- to 10-pound weight gain over the course of 1 year.
Evaluation of obesity in childhood is important for preventing disease progression with its associated morbidities into adulthood. These morbidities include hypertension, type 2 diabetes mellitus, hyperlipidemia, hyperuricemia, and some forms of cancer. Obesity may also have a negative impact on self-esteem of children and adolescents.
Although genetic and hormonal causes of obesity are rare, they do warrant consideration in obese children. It is important to differentiate between endogenous and idiopathic causes of obesity. Endogenous causes represent fewer than 10% of all cases of pediatric obesity. With endogenous causes, the child is typically of short stature (less than the 10th percentile), often is mentally impaired, may have delayed bone age, and there is no family history of obesity. In idiopathic cases, the child usually has normal stature, a family history of obesity, normal mental function, normal or advanced bone age, and a normal physical examination.
• Antipsychotic agents
• Corticosteroids
• Cyproheptadine
• Methimazole
• Progestins
• Propylthiouracil
• Valproate
Only a small percentage of cases of childhood obesity are associated with a hormonal or genetic defect, with the rest being environmental or idiopathic in nature.
Hormonal Causes
• Acquired hypothalamic problems (brain injury, brain tumor, cranial irradiation)
• Cushing’s disease
• Hypothyroidism
• Primary hyperinsulinism
• Pseudohypoparathyroidism
Genetic Causes
Instant Work-ups A Clinical Guide to Pediatrics
