Purpose of review: When evaluating the causal link between obesity and the development of asthma in children, prospective cohort studies are essential. The results of the most recently published birth cohort studies from Sweden, Germany, Brazil, Belarus, and California, USA, as well as from a joint analysis of eight European birth cohorts of the Global Allergy and Asthma European Network are evaluated. Moreover, the results of two meta-analyses are presented.
Recent findings: Most recent prospective cohort studies found a dose–response association between overweight or obesity and asthma. The evidence of effect modification by sex, ethnicity, and age was inconsistent. Both meta-analyses also showed that overweight children were at an increased risk of incident asthma compared with nonoverweight children and that the relationship was further elevated for obesity.
Summary: Prospective cohort studies and two recently published meta-analyses found an association between overweight (and especially obesity) and asthma in the appropriate temporal sequence and in a dose–response manner. Children with a pronounced weight gain slope in early life were particularly at risk for asthma within the first 6 years of life. The gain in BMI over time during infancy may be an even more important predictor for asthma in childhood than excess weight at any specific age.