The many campaigns that have been waged over the past decade to get American children to avoid unhealthy foods have not been fruitless. The national childhood obesity rate has stopped rising. Yet neither is it falling. What kids need is not just a better diet, but also a better media diet.

The U.S. childhood obesity rate stands firm at 17 percent. And many overweight children and adolescents in the U.S. are growing even heavier. The number who are severely obese -- with a body mass index of 35 or even 40 -- has reached 4.6 million. Reducing childhood obesity will require moving beyond school-based strategies to address what and how much kids eat at home.

One way to do this is with a soda tax, such as the one proposed in Philadelphia which is now at the center of a disagreement between the Democratic presidential candidates. Hillary Clinton has endorsed the local effort to put a 3-cents-an-ounce tax on sugary beverages, while Bernie Sanders has denounced it because its burden would fall most heavily on the poor.

What Sanders fails to acknowledge is that the benefit of the tax would also be greatest for the poor -- and their children -- who consume a large share of sugary drinks. A nationwide soda tax could lower consumption of sugary drinks by 20 percent, according to one model. To offset the measure's regressive cost, Philadelphia and other cities and states considering soda taxes should spend the revenue on other obesity-prevention campaigns in poor neighborhoods.

Another approach is to limit the advertisements for high-calorie, low-nutrition foods that children see on television and online. Evidence accumulated over decades demonstrates that such ads cause children to eat more. Yet public-health efforts to get food makers to cut back on the ads have faced overwhelming resistance, while the food industry's modest voluntary strategies have been ineffective.

At the very least, companies should not get a tax break for advertising junk food to children. (Under the current tax code, advertising and marketing costs are deductible expenses.) A bill that would eliminate this deduction, which died in the last Congress, should be re-introduced and passed.

Finally, doctors need to come to a consensus about how best to prevent and treat childhood obesity, as specialists have for adult obesity. The average primary care doctor has as many as 50 severely obese children in his or her practice. Too often doctors neglect to counsel children (and their parents) to avoid high-calorie foods and long hours in front of the TV or computer, under the influence of food ads.

Obese kids suffer all sorts of ill effects, from high blood sugar to low self-esteem. More often than not they turn into obese adults. Saving their lives -- not to mention billions of dollars in medical costs and lost productivity -- is going to take a more aggressive and concerted effort.