...that chronic mold exposure in your house, work or school can lead to obesity?

The mechanism appears to be through the development of Leptin resistance. Leptin is a molecule secreted from the gut that --- inhibits food intake and activates thermogenesis in conjunction with insulin. Chronic mold exposure activates a part of the immune system (innate immune system) which leads to damage to the Leptin receptors in the brain. This Leptin resistance leads to weight gain.