The aim of this article was to evaluate the effects of circulating leptin in asthmatic patients with obesity by carrying out a systematic review and a meta-analysis in order to check whether some potential treatments (e.g., leptin inhibitors) may be useful in the future to ameliorate asthma symptoms in obese patients or even achieve a complete remission of the disease. This evidence concerns the gene LEP and obesity due to melanocortin 4 receptor deficiency.