To answer simply, it would be hard. Most people have been eating unhealthy food for a long time. To change family eating habits, you would either start cooking for them and show them how to do it or show them the negative consequences of eating junk food. I would introduce a few changes: I would eliminate takeaway food, reduce the amount of meat consumed, and start using more vegetables.
It's a complicated problem. One of the reasons needs to be a tremendous amount of takeaway junk food. Pandemic doesn't make problems smaller; on the contrary, it makes the problem bigger. Young people are not exercising government is happy when they just stay home and don't move outside. Every one of these factors is partaking in overweight.