Overweight preschoolers have a grater risk to develop asthma by the time they are 7-years old, but losing weight early on may counter this risk.

Researchers feel there may be several biological explanations for the link between being overweight and asthma.
One possible explanation may involve the hormone leptin, which is derived from fat and is found in higher amounts in people who are overweight and previous studies have suggested that leptin may cause exaggerated inflammatory responses by the immune system, which is a key feature of asthma.
The study has been published in the journal Pediatrics.
Source-Medindia