Obesity

Published on 21/03/2015 by admin

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Chapter 34 OBESITY

Jonathan M. Wong

General Discussion

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.

Medications Associated with Childhood Obesity

• Antipsychotic agents

Key Historical Features

Nutritional history

• Breastfeeding or formula

• Duration of breastfeeding

• Age at introduction of solids

• Caloric intake

• Dietary quality in terms of nutrient balance and food groups

Level of physical activity

Limitations because of weight

Amount of sedentary activity such as watching television or playing video games

Respiratory difficulties such as snoring and somnolence

Perinatal history

• Birth weight

• Maternal gestational diabetes

Past medical history

• Diabetes

• Asthma or breathing difficulties

Menstrual history in females

• Cardiovascular disease

Social history

• Living situation

• Socioeconomic status

• Who prepares the food

• Frequency of dining out or eating fast food

• Tobacco use

• Alcohol use

Key Physical Findings

Vital signs, including blood pressure

Height and weight

Evaluation of the growth curve

May consider triceps skin fold

General evaluation to assess for any dysmorphisms

Head and neck examination for tonsillar hypertrophy or thyroid goiter

Pulmonary examination for evidence of asthma, decreased air exchange, or hypoventilation syndromes

Abdominal examination to evaluate for central versus peripheral obesity or right upper quadrant tenderness suggesting the presence of gallstones

Musculoskeletal examination to assess for stress on the joints, especially the knees

Genitourinary examination to evaluate for hypogonadism

Neurologic examination to evaluate mental status and evidence of any genetic syndromes

Skin examination for acne, acanthosis nigricans, fungal infections, or striae

Vision and hearing screening if a genetic syndrome is suspected

Suggested Work-up

If the history or physical examination suggests an endogenous cause for obesity, the work-up should be guided by clinical suspicion.

Fasting blood sugar	May be indicated in obese children because the rates of juvenile-onset type 2 diabetes mellitus are rising
Fasting lipid panel	The National Cholesterol Education Program Expert Panel on Blood Cholesterol Levels in Children and Adolescents recommended screening in all obese children over 2 years of age
Thyroid-stimulating hormone (TSH) and free thyroxine (T₄)	To evaluate for hypothyroidism
Dexamethasone suppression test and 24-hour free urinary cortisol level	If Cushing’s disease is suspected
Fasting blood sugar, plasma insulin, and C-peptide levels	If hyperinsulinism is suspected
Calcium, phosphorous, and parathyroid hormone (PTH) levels	If pseudohypoparathyroidism is suspected
Brain imaging	If a hypothalamic cause is suspected
Genetic testing/chromosomal analysis (genetic syndromes)	If a genetic syndrome is suspected

Additional Work-up

Follicle-stimulating hormone (FSH) and luteinizing hormone (LH)	If polycystic ovary syndrome is suspected
Sleep study	If sleep apnea is suspected
Pulmonary function tests	If asthma is suspected
Liver function tests	If nonalcoholic fatty liver disease is suspected
Right upper quadrant ultrasound	If cholelithiasis is suspected