Incidence of Obesity In The World
Obesity is the most prevalent nutritional disorder among children and adolescents in the United States. Approximately 21-24% of American children and adolescents are overweight, and another 16-18% is obese; the prevalence of obesity is highest among specific ethnic groups.
Childhood obesity predisposes to insulin resistance and type 2 diabetes, hypertension, hyperlipidemia, liver and renal disease, and reproductive dysfunction. This condition also increases the risk of adult-onset obesity and cardiovascular disease.
Obesity in children is a complex disorder. Its prevalence has increased so significantly in recent years that many consider it a major health concern of the developed world. The National Health and Nutrition Examination Survey (NHANES) indicates that the prevalence of obesity is increasing in all pediatric age groups, in both sexes, and in various ethnic and racial groups. Many factors, including genetics, environment, metabolism, lifestyle, and eating habits, are believed to play a role in the development of obesity. However, more than 90% of cases are idiopathic; less than 10% are associated with hormonal or genetic causes.
- Using body mass index (BMI) criteria, the most recent national surveys demonstrate that 21-24% of American children and adolescents are overweight and that another 16-18% are obese. A 2012 study noted a 16.9% prevalence of obesity in children and adolescents in 2009-2010, which is comparable to the prevalence rates reported in 2007-2008.  These findings indicate that the prevalence of overweight (BMI ≥ 85th percentile) children and adolescents in the US has increased by 50-60% in a single generation, and the prevalence of obesity has doubled. The prevalence of obesity in American Indians, Hawaiians, Hispanics, and blacks is 10-40% higher than in whites.
- International data reporting regarding childhood obesity varies, and accuracy may be less than optimal; however, Eneli and Dele Davies reported that in 77% of the countries analyzed, the prevalence rate for children who were overweight was at least 10%. Notably, the highest rates for children at risk for obesity were found in Malta (25.4%) and the United States (25.1%). Lithuania (5.1%) and Latvia (5.9%) had the lowest rates. A recent European Youth Heart Study suggests Swedish children have a lower risk of becoming overweight or obese in adolescence compared with Estonian children.
- Race and ethnicity are associated with increased rates of obesity in children and adolescents. Puerto Rican, Cuban American, and Native American preschoolers have an increased incidence of obesity; black, Native American, Puerto Rican, Mexican, and native Hawaiian school-aged children have the highest rates of obesity in this age group. Approximately 25% of black adolescents are obese. Rosen reported that obstructive sleep apnea hypoventilation (OSA/H) is more commonly seen in black children than in Hispanic or white children. Tonsils and adenoids are at their peak size, relative to the size of the oropharynx, when children are aged 2-7 years.
- During the second decade of life, females are more likely to be obese than males, except for black teenagers, among whom males are more likely to be obese than females. Although the male sex is associated with an increased incidence of OSA in adults, no differences have been identified in children before puberty.
- Adolescent obesity is predictive of adult obesity, with 80% of teenagers who are obese continuing on to be obese as adults. Obesity is more likely to occur during specific periods of life, such as when children are aged 5-7 years and during adolescence. A recent European Youth Heart Study suggests male sex confers a higher risk of obesity in adolescence.