OP, I asked this exact question when I renewed my passport 2 years ago - for a 10 year one. I asked because based on my then current age I fully expected a major decline in appearance in 10 years - nothing to do with weight loss etc.

I was told that the new Canadian 10 year passports use data points on a person's face. Whether this is true or not I do not know but I am hoping it is. However, it was very good news for the people behind me who had multi-coloured hair - as in yellow, pink and blue. My husband asked the same question when he renewed his passport last year and was told the same.