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.

In a proverbial chicken vs. egg scenario, doctors often don't know if the constricting of airways caused by asthma causes kids to not want to exercise, and therefore to gain unhealthy amounts of weight, or if it is because kids are overweight that their airways narrow and they develop asthma.

"Most kids who suffer from asthma also have allergies," said allergist Michael Foggs, MD, ACAAI president. "These allergic responses in the lung can lead to symptoms of allergy. Coughing, wheezing and shortness of breath are all symptoms that make exercise harder. We work with our asthma patients to make sure they are breathing well enough to exercise and play."

According to ACAAI, children with asthma and other allergic diseases should be able to participate in any sport they choose, provided the allergist's advice is followed. Asthma symptoms during and immediately following exercise may indicate poorly controlled asthma.