Why are children becoming obese?

The presence of obesity in at least one parent significantly increases the risk that an obese child will become an obese adult.

While there are genetic conditions which predispose or even cause children and adolescents to become overweight or obese, it is usually not the primary reason for weight problems in this country. In fact, only a small percentage of childhood obesity is associated with a hormonal or genetic defect. Children, like adults, mostly gain weight when energy input (food) exceeds energy output (exercise).

Interestingly, studies have shown that on average, some overweight or obese children do not consume significantly more calories (food) than their thin similarly aged counterparts. In simplistic terms, it is not that they are eating more, but rather doing fewer activities. This leads to a positive energy state in the body, which will result in weight gain.

So a relatively small imbalance between caloric intake and energy or physical output can lead to significant weight gain over time. This is what is scene, with most obese children demonstrating a slow but consistent weight gain over several years. Fortunately, diet and physical activity are susceptible to behavior modification, and the first step is weight awareness.

Examples of Genetic Causes of Childhood Obesity
Hormonal causes	Diagnostic clues
Hypothyroidism	Increased TSH*, decreased thyroxine (T4) levels
Hypercortisolism	Abnormal dexamethasone suppression test; increased 24-hour free urinary cortisol level
Primary hyperinsulinism	Increased plasma insulin, increased C-peptide levels
Pseudohypoparathyroidism	Hypocalcemia, hyperphosphatemia, increased PTH* level
Acquired hypothalamic	Presence of hypothalamic tumor, infection, syndrome trauma, vascular lesion
Genetic syndromes	Associated characteristics
Prader-Willi	Obesity, unsatiable appetite, mental retardation, hypogonadism, strabismus
Laurence-Moon/Bardet-Biedl	Obesity, mental retardation, pigmentary retinopathy, hypogonadism, spastic paraplegia
Alström	Obesity, retinitis pigmentosa, deafness, diabetes mellitus
Börjeson-Forssman-Lehmann	Obesity, mental retardation, hypogonadism, hypometabolism, epilepsy
Cohen	Truncal obesity, mental retardation, hypotonia, hypogonadism
Turner's	Short stature, undifferentiated gonads, cardiac abnormalities, webbed neck, obesity, 45, X genotype
Familial lipodystrophy	Muscular hypertrophy, acromegalic appearance, liver enlargement, acanthosis nigricans, insulin resistance, hypertriglyceridemia, mental retardation
Beckwith-Wiedemann	Gigantism, exomphalos, macroglossia, visceromegaly
Sotos'	Cerebral gigantism, physical overgrowth, hypotonia, delayed motor and cognitive development
Weaver	Infant overgrowth syndrome, accelerated skeletal maturation, unusual facies
Ruvalcaba	Mental retardation, microcephaly, skeletal abnormalities, hypogonadism, brachymetapody
Gene associations
Leptin
Beta3-adrenergic receptor
TSH=thyroid-stimulating hormone; PTH=parathyroid hormone.

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