You are quite right about the importance of calcium in building strong bones for the future. It might help your girls to think about their bones as bone banks. Right now they can make deposits of calcium to build bone mineral density. Later in life no further deposits are allowed. That's when the body starts withdrawing bone leading to conditions like osteopenia and osteoporosis.

It's also true that although teenagers can stop growing taller, bone mass hasn't peaked yet. Skimping on calories should be done by eliminating sugar-filled food items, not calcium-rich foods. Yogurt instead of ice cream or low-fat milk instead of milk shakes is advised.

If your girls won't listen to you, make an appointment with their pediatrician or your family doctor. Explain your concerns ahead of time and let the health care experts take it from there. Your children may not change their eating patterns, but you will have done everything you can and should do as a parent. The rest is up to them.