As you are responsible for the food in your home you have a good chance of helping your family with their weight problems. I will make several suggestions, but it is important that changes always happen gradually, as this gives them time to get used to new eating habits and like them. For you and Maria, it can also mean some changes in your eating habits.
Those who are naturally slim eat what they need and then they don't want to eat any more.
Hopefully, you can use the following suggestions if you think you can avoid trouble with your husband and Joanna.
1. Never comment on your husband's and Joanna's eating as it only leads to a power struggle where they can blame you instead of concentrating on their own problems.
2. Don't bake any more cakes. Offer your guests herbal tea or cappuccino (milk, coffee powder and a little fructose which is warmed up and then whipped).
3. If possible serve porridge at breakfast, but only in suitable amounts for each person. Try to avoid having bread, butter, cheese and sausages at home.
4. Don't serve more food for dinner than each person ought to have, but serve a large salad so everybody can satisfy their hunger.
5. Try to help Johanna with her junk food problem by giving her a bag of fruit to eat at school and telling her not to take any money with her.
6. The guideline is that any food which is overeaten should not be kept in the house, but replaced by greens and fruit so that everybody can be satisfied.