South Carolina lawmakers are focusing on the waistline of state students these days; consequently, they want to limit the availability of certain food items in school vending machines.

A senator from the S.C. Piedmont says schools are sending mixed messages to students. On the one hand, students are taught they should eat nutritious foods. On the other hand, they are inundated with a variety of unhealthy foods in vending machines.

The legislation seems an attempt to join forces with a Childhood Obesity Prevention Campaign launched by Commercial Alert and endorsed by dozens of organizations and scholars. Their goal is to prevent marketing, distribution and sale of junk food in schools, and to improve the quality of food provided to students.

The campaign's goal is noble, but getting junk food out of schools will be somewhat more difficult.

There is little doubt that U.S. children as a group suffer from obesity. Studies have indicated an increase in obesity for years. Junk food is a major culprit. Video games and television are contributors. Efforts to get students to exercise more extend back to at least the administration of John F. Kennedy. Exercise was a key ingredient of improving the health of America's youth then, as it is now. Over the last 40 years, fast food and vending machines have proliferated in communities and schools.

According to the Centers for Disease Control, about 4.3 percent of U.S. boys and 3.6 percent of U.S. girls between the ages of 6 and 11 were overweight in the early 1970s. The number has nearly quadrupled today as 16 percent of boys and 14.5 percent of girls in that age range are considered overweight. Older children also have recorded an increase in weight, the CDC states.

Commercial Alert says that junk food purveyors are using public schools as a platform for their marketing campaigns. "In effect, the junk food lobby has latched onto the compulsory school laws as a way to corral a captive audience of impressionable children," Commercial Alert says.

A healthy diet is important for a number of reasons: more energy, cancer prevention, diabetes prevention, prevention of heart attack. The list could go on and on.

Hurdles confronting lawmakers, doctors and school administrations in their effort to curb obesity are several fold:

Changing social attitudes about junk food will take decades and generations, not weeks or months;

Weaning school administrations and athletic departments from the use of vending-machine revenue will be just as difficult as changing a kid's mind about a candy bar and soda versus a bottle of water and a carrot; and

As school budgets shrink, the dependency upon vending machines as a source of revenue for extracurricular activities may increase.

The Chester County senator who sponsored the legislation to revise junk food policies included a valuable idea, though. Linda Short would have schools offer students through the eighth grade at least 150 minutes of physical education a week. The 30 minutes of physical exercise a day may be more than most get now.

The bottom line is that it will be difficult to get more nutritious foods in the machines or to get them out of schools. Teaching kids about nutrition is an ongoing action and it must start at the cradle.