Not just in your family but in the general public, there seems to be an "understanding gap" between the notion of weight loss and the pursuit of optimal health.
How many of us have heard "Stop dieting, you're thin enough" or "Why do you run, you're already thin".
There is a difference between shrinking to smaller and becoming stronger, faster, able to work all day without flagging.
And trust me ... you can talk yourself blue in the face and they still won't hear you.
Gently, calmly ... you'll have to prove your mettle

When they see that your life is full ... lots of energy, glowing good health, internal happiness, balance, they'll know that you've made wise decisions.
If all of this is making you wonder if you are obsessing, talk it out here and at home. You're very fortunate that your parents love and care for you. You don't have to disregard them. Their observations are very important. Consider them another tool ... like your reflection in the mirror, the scale, your tape measure ...