Role Model to the children

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I am a mother of two daughters and i felt i failed them to be fit and stay healthy. I lost 15 pounds but they gained weight. I mean our calories is between 1200 to 1800 but most of the day, they will be at the daycare or school so the time i get them, it will be dinner and dessert. They are very active-choir, dancing, cheerleading, riding bikes, exercise with me in the living room so why cant they lose weight? I am still having trouble doing portion control with the girls and what supposed to be on the plate for them to eat healthy.