Obesity and overweight are terms that are commonly used interchangeably in children, with overweight being the preferred term. As the prevalence of overweight has increased in children and adolescents, complications of overweight are now well recognized in children.

Pathogenesis:

Overweight results from a dysregulation of caloric intake and energy expenditure. A complex interplay between each individual’s genetic predispositions and the environment affects an intricate system that controls appetite and energy expenditure. Prehistoric ancestors of humans experienced long periods of food scarcity, so energy conservation and storage during times of food availability had a survival advantage.

Diagnositic Criteria for Overweight:

The diagnosis of obesity in adults is based on calculation of the BMI by dividing the weight in kilograms by the height in meters squared (kg/m²). The calculated BMI can overestimate adiposity in trained athletes or muscular children, but it is generally recognized as the most reliable method to determine healthy and unhealthy adiposity. Other methods of determining adiposity are useful, but are either too expensive to be of practical use in a clinical setting (ultrasound, CT, MRI, DEXA, total body conductivity, air displacement plethysmography), require specialized training (skinfold thickness), have poor reproducibility (waist-hip ratios), or lack extensive normative data in children (bioelectric impedance analysis). Therefore, BMI in combination with clinical assessment is sufficient to make the diagnosis.

Children’s adiposity rises in the 1st year of life, reaches a nadir around 5–6 yr of age, and then increases again throughout childhood. This is called the adiposity rebound. The 95th percentile BMI for a 4 yr old is approximately 19, but it is 25 in a 13 yr old. Consistent use of the BMI growth Continue reading »

Thiamine (vitamin B₁) provides the functional group for the coenzyme thiamine pyrophosphate, which is involved in decarboxylation of pyruvate and ?-ketoglutarate and, thus, is important in the release of energy from carbohydrates. It also participates in the hexose monophosphate shunt that generates nicotinamide adenine dinucleotide phosphate and pentose.

Thiamine also is required for the synthesis of acetylcholine, and deficiency results in impaired nerve conduction.

Good sources of thiamine include meat (especially lean pork), legumes, and cereals. Unless enriched, refined cereals and flours have a much lower content of thiamine than whole grains. The vitamin is easily destroyed by heat, particularly in alkaline media, and significant amounts are lost in discarded cooking water. The breast milk of a well-nourished mother provides adequate thiamine; breast-fed infants of thiamine-deficient mothers, however, are at risk for deficiency. Most infants and older children obtain an adequate intake of thiamine from food and do not require supplements.

Thiamine is absorbed efficiently in the gastrointestinal tract, but may be decreased in persons with gastrointestinal or liver disease.

Deficiency (beriberi) has been reported in adolescents after gastric bypass surgery. Intakes in excess of tissue needs are excreted in the urine. Fever and/or stress may increase the requirement for thiamine and unmask marginal thiamine sufficiency, but these factors are unlikely to cause deficiency.

Thiamine dependence has been described in a child with megaloblastic anemia and in an infant Continue reading »