Dear Jeff,

With the national focus on preventing childhood obesity, my sister has asked me to make sure my niece and nephew don't drink soda when they are in my care. Is it really that bad for them? Or is it okay if I allow them to have it as a special treat from time to time?

Childhood obesity is indeed a serious problem. While there are many complex and controversial explanations for it, the bottom line is pretty straight-forward: anyone who consumes more calories, from any source, than they burn, is going to have a problem.

Sugar sweetened sodas provide lots of calories and no nutrients. There's nothing wrong with that once in a while, especially for more active children, but it is important that your nieces and nephews not overdo it.

But while your sister is right to be concerned about her kids' caloric intake, focusing exclusively on soda is a mistake. Juices have lots of calories too, and rarely provide much in the way of needed nutrients. The same can be said for lots of other "fun foods" or beverages.

If your sister is concerned about calories from soda, she should consider allowing her kids to enjoy diet sodas. These options are absolutely safe and often just as refreshing as the real thing.

I recommend that you have a conversation with your sister about the different ways to help your nieces and nephews stay fit.

Jeff Stier is the Associate Director of the American Council on Science and Health (ACSH).