Childhood asthma and obesity—what is the true link?

Abstract

Obesity rates have increased significantly in children in many parts of the world, especially in North America.1 According to data from the most recent National Health and Nutrition Examination Survey, approximately 17% (or 12.5 million) of US children and adolescents 2 to 9 years old are obese.2 The impact that childhood obesity has on pediatric diseases has become a major prevention initiative by the Obama administration and several public health organizations. Children with obesity are at increased risk for developing asthma, one of the most common chronic diseases in children.3 Childhood asthma accounts for more than 14 million missed school days per year and is the primary cause of school absences in the United States.4 A relation between obesity and asthma is supported by prospective studies in adults and children suggesting that being overweight and obese can precede the onset of asthma5 and studies in adults showing alleviation of asthma symptoms with weight loss.6 Despite consistent evidence linking obesity to the incidence and prevalence of asthma and several postulated hypotheses to explain this association, a definitive mechanism remains a mystery. Genetic and Environmental Factors Asthma and obesity are likely to be connected in a multifactorial fashion. Although genetic susceptibility can contribute to the development of asthma and obesity, the rapid increase in a relatively short period suggests that changes in lifestyle, such as diet, physical activity, early life exposures, and other environmental interactions, also can play a role. Epigenetic mechanisms associated with obesity and asthma have been proposed. Obesity and asthma likely have their beginnings in utero and in early childhood. Diet and nutrition, especially prenatal and early infant diet, may play a part in these diseases. Greater consumption of fruits and vegetables, antioxidants, minerals and vitamins, fish, and legumes during pregnancy seems to confer protection against childhood asthma and wheeze7 and may influence the neonatal immune system and lung development.8 However, 1 study showed that fatty acid dietary supplementation during pregnancy did not lower the overall incidence of asthma.9 To further support the idea that intrauterine nutrition is important, associations between low birth weight and resulting obesity and asthma have been shown. In 1 study, low birth weight led to the development of asthma and excess body mass increased the risk.10 Rapid growth in body mass index (BMI) during the first 2 years of life increased the risk of asthma up to 6 years of age based on published data from 8 European birth cohorts.11