My kids are the same way. I no longer mention anything at all....however by leading through example a subtle pressure is applied that leads them to hopefully question their choices. (you are losing they are not...gee whats wrong?).....I bring up primal and I get "Im not giving up, X or Y or Z....Okay so dont your the one that is overweight not me.... or so the conversation plays out time and again as I continue to shrink down to normal human size. I hope by Xmas to really put the pressure on them through the back door so to speak.
They used to call me No Neck, but now I have one.