Do yummy mums REALLY need to go to the gym?

Today my son put me on something of a guilt-trip. After seeing a photo of my husband and I, he declared: "that must be a really old photo mum! How old were you then?""Why must it be old?" I asked."Because you look so much younger on that photo, Mum! You weren't fat then..." What?? Fat?? The photo was only taken four years ago, and surely...