How do you answer the question in a job interview 'Why are you looking for a change'?

Why are you looking for a change? To avoid stagnancy, after (number of years) at (company name) i stopped being challenged and my satisfaction at the end of the day gradually became less and less. Change is necessary, not for the sake of it, but if one has no job satisfaction then different challenges are needed. I love to learn, and i love being challenged. That is what i hope to find here.