Can you fire an employee because you "think" their obesity is a disability? The EEOC doesn’t think so and filed a lawsuit (pending in federal district court) alleging that a company did just that.
Before the ADAAA, EEOC needed to prove that the employer was aware of a physical impairment that substantially limited life activities. Now, post ADAAA--EEOC needs to show only that the decision makers knew of or believed that its employee had a physical impairment.
I think employers can expect to see more lawsuits alleging discrimination based on actual or perceived conditions. Adverse employment actions, such as termination, can be potential "high risk" situations. Make sure you can defend your actions and remember to DOCUMENT…DOCUMENT…DOCUMENT every step of the way.