For years, doctors have known that there is a link between childhood obesity and asthma, but have found it difficult to determine which condition tends to come first, or whether one causes the other.

An article published in the September issue of Annals of Allergy, Asthma and Immunology, the scientific publication of the American College of Allergy, Asthma and Immunology (ACAAI), suggests it is more probable that childhood obesity contributes to asthma, although the connection is complex and has many factors.

“The relationship between obesity and asthma in adults, which shows that being overweight and obese can precede the onset of asthma, is supported by a number of studies,” said allergist Perdita Permaul, MD, lead author. “There isn’t as much evidence for children, but the progression from obesity to asthma, rather than the other way around, seems probable.” The article cites a study that showed that 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. It has also been shown that the onset and duration of obesity and the composition of the excess fat – lean vs. fat – can affect lung function.