Your prospective employer is not calling you in to ask you about the gaps in your work history--he/she wants to talk to you because something that you did was something that they needed--if you are asked about the gaps, it will likely be just in passing, so a simple and unebellished answer is best("The job market was slow, and I was sidetracked by some health problems, but they're resolved, and I am back on track")--

The truth is that if some people were honest about their work environments, they would say,
"It helps to be an alcoholic if you work here"--which is why you want to check the employer out even more carefully than they check you out--