Close offices and as many other places as possible at lunch time on a Wednesday to enable free/funded sport experiences to happen, Let people fall in love with exercise, too many people have only experienced sport as a compulsory school event but they might love tennis or golf or netball, make this accessible for all, including school children, transport provided if possible.
Education, family cooking classes if possible, if not, making real life meals at school, providing casserole packs really cheaply for eg.
A focus on understanding the link between good diet and mental health from young children up, not paying lip service, a real sustained and focussed effort from adults in education.
Supporting families to have the time to cook well balanced meals, exactly as a previous poster said, I come home from a week of teaching and end up getting a beige tea together, creating healthier quick food, so if your child has an activity straight after childcare, you don't have to give them a sausage roll in the car!
The final one I don't know how to achieve but to change mindset about food as a reward, it's so ingrained in our culture!