Walt Disney is the latest company to jump on the childhood anti-obesity band wagon. Today Disney will announce a new initiative to advertise healthier food products on all its media platforms for children. The company says that ads for sugary cereals and junk foods will eventually be phased out, and by 2015 all companies advertising food products with Disney will be required to comply with new nutritional standards.

Ever since Joseph Priestly discovered how to "impregnate water with fixed air" in the 18th century, carbonated beverages have been ubiquitous. Sodas have been used to cure diseases, fight alcoholism, and spread American culture around the globe. On this week's Please Explain, we’ll find out what soda is, what’s in it, and when it became so popular. We’re joined by Dr. Kelly Brownell, the co-founder and director of the Yale Rudd Center for Food Policy and Obesity, and Darcy O'Neil, beverage master and author of the book Fix the Pumps, a history of soda from the 18th century to the present.

According to recent studies, about 1/3 of Americans are obese, and between 1998 and 2006, the obesity rate rose 37% in this country. Obesity-related illnesses accounted for an estimated $147 billion in 2008, nearly 10 percent of all U.S. medical spending, according to the Centers for Disease Control. On today’s ...