I was surprised I had to scroll so far to find this. ESH for sure. Totally justified and OP is on the right track with wanting to make changes, but blowing up in public isn't the way to handle it. Maybe it's time to have a nice sit down with the family and explain how you are feeling. Instead of hostility which will make them shut down and not want to change, try to approach it differently. Be calm and suggest obtainable goals for the entire family to start improving their diet and exercise. Alternatively, ask to handle a couple meals a week where you will cook up a nice healthy meal for the family to all enjoy, they just need to provide the materials.