Does God care about our weight? Yes, I believe that He does because He cares about us and the practicalities of our lives, but His greater concern is if our perception of our weight, or any identity, desire, or distraction, replaces His view of us.
Happiness is not the goal of life. Happiness is a feeling—joy is a state of being. God wants us to have joy, which is that special place of resting in the hope and truth that God is and always will be.