The findings are based on almost 6,000 adults taking part in the Third National Health and Nutrition Examination Study, which assessed the health and nutrition of US citizens.
The researchers measured the levels of leptin, an inflammatory protein that is produced by fatty tissue in the body.
Leptin levels were significantly higher among those who had been diagnosed with asthma, than those who had never had the respiratory disease.
After taking into account various factors likely to influence the findings, the association between leptin and asthma appeared to be stronger in women than in men, and stronger in women who had not yet gone through the menopause.
Although heavier women had a greater risk of asthma, this was not explained by their high leptin levels.
This suggests that the protein may not be responsible for the link between overweight and asthma, but may have an independent role in increasing the risk for the disease, say the authors.
Thorax