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To avoid developing asthma fat children should lose weight. A large cross sectional study of children in the United States confirms that obesity increases the likelihood of asthma, but not atopy, as an independent risk factor.
Previous studies linking body mass index (BMI) and respiratory symptoms including asthma have been called into question by the recent finding that breastfeeding, which protects against asthma and atopy, is strongly inversely related to BMI in children starting school and is therefore a potential confounder.
Von Mutius et al sought to determine whether the apparent association between BMI and asthma is a true one by analysing data on more than 7000 children from the National Health and Nutrition Examination Study (NHANES) III and data collected for a comprehensive range of variables. Among these were prevalence of asthma and atopy and a whole array of known or potential confounders including birth weight (children aged <12 years) and breastfeeding (children aged <6 years).
Prevalence of asthma and atopy increased significantly across the quartiles of BMI. The relation held true for asthma after adjustment for potential confounders—age, sex, ethnicity, household size, and passive exposure to smoke—and after further controlling for breastfeeding and birth weight. No independent relation was seen between BMI and atopy. As cause and effect cannot be determined by a cross sectional study, the authors point to evidence from studies over time in nurses and children in support of their conclusion—that obesity predisposes to asthma.