Weight can be a real touchy issue for women in particular. While you may be providing good advice, you may be alienating your fiance. You know the saying about leading a horse to water, but you can’t make him drink? You also need to allow her individual approach in spite of your concern for her as long as she is not doing something life-threatening. You, however, can model healthy eating habits.
Instead, create opportunities for you two to exercise together. Make it fun like walking, biking, rollerblading or even shopping. Choose exercises that she likes so she is more likely to participate. Don’t make a point by saying that you are trying to get her to exercise. Just provide the opportunity and see if she responds to it.
Second, when you go out to eat or cook together, plan meals that have a variety of foods, but low on the sweets and desserts. Limit alcohol as your body turns it to fat in order to metabolize it. Don’t dangle foods in front of her that will increase her weight. Remember if you don’t buy it or cook it, food has a hard time finding its way into your mouth. So if you live together, together get rid of salty snack foods, sweets, and desserts. Set up your home environment for your fiance to succeed.
The one exception is on either of your birthdays, definitely, have cake. Grocery stores usually have individual slices of cake, pie, and dessert. Same is true if you go out to eat on your birthdays.
She’ll definitely need your support when she goes off the low carbohydrate diet. You can’t eat that way forever.