“Every parent is a sucker when it comes to children.”

That, according to Bettina Elias Siegel’s book, “Kid Food: The Challenge of Feeding Children in a Highly Processed World,” was the gist of a journal article entitled “Advertising to the Child to Reach the Parents.”

It was published in 1933.

Food manufacturers have spent a good part of the past century figuring out how to get kids to convince their parents to spend money, and they’ve gotten very good at it. New York University professor Marion Nestle, who has been following the issue for decades, told me she hears from parents about junk food marketed to children all the time. “Parent after parent says they don’t have it in the house, they don’t buy it, but their kids tell them they want it. How do they know this?”

The frequency with which she hears that makes restricting ads to kids Nestle’s top priority in the fight against childhood obesity. “It’s the first thing that needs to be done.”

I have not found a dissenter in the public health community. Nearly everyone wants the government to restrict the foods that manufacturers can advertise to children. But would that reduce childhood obesity? Other countries have tried it, so we should have some idea.

I took a hard look at what we’ve learned, and checked in with several people who study public health policy. There’s a lot that people agree on, which will save both you and me from slogging through mounds of evidence trying to figure out what’s true. Here’s what we know:

● There’s strong evidence that ads influence kids.

● There’s a lot of suggestive evidence that restricting ads affects kids’ diets.

● Restricting ads hasn’t been causally linked to a decrease in childhood obesity.

Research aside, there’s one very good reason to believe advertising works: Food companies spend billions doing it. In 2009, the Federal Trade Commission looked at ad spending and found that food and beverage companies targeted kids to the tune of $1.8 billion that year. (I haven’t found more recent aggregated data.) Siegel’s “Kid Food” documents how deliberate, and how successful, marketing campaigns aimed at getting kids to bug their parents are.

Still, the answer to the all-important question of whether restricting ads would reduce obesity is a resounding “probably, a little.”

Is that good enough? If you ask the public health community, it is. As the City, University of London’s Corinna Hawkes wrote in a recent blog post on the subject, “We have to act despite uncertainty.” Parke Wilde, a professor at Tufts University’s Friedman School who studies food policy, was on the same page. Expecting ironclad evidence that restricting ads cuts obesity is, he told me, “a hurdle that can’t be met.” The effect would be too small to tease out of population-level data.

But woven into all the arguments about what to do about Americans’ diets is another all-important question: Are diets something the government should get involved in? When then-New York City Mayor Mike Bloomberg tried to reduce soda sizes, there was pushback from people who thought they were perfectly capable of choosing a soda size for themselves, thank you very much. (The measure was enacted, but struck down by the state supreme court.)

Walter Olson, senior fellow at the libertarian think tank the Cato Institute, opposed the soda restriction and has several reasons for opposing advertising restrictions. First, he told me in an email, it’s censorship (whether the Supreme Court would agree probably depends on who’s on it). It also “overrides parents, who have a range of views. . . . Where does the government get off banning messages we don’t mind?”

Restricting junk food ads also gets the government into drawing a lot of arbitrary lines, Olson wrote. What is junk food? What age group are we talking about? Which media are we restricting? Those are good and important questions, and the answers may determine whether the law is effective.

Food manufacturers are endlessly adaptable. Whatever definition of junk you adopt, you can bank on a tidal wave of foods that just barely qualify as not junk. That’s what happened in schools when a new suite of nutrition standards went into effect in 2014. Copycat versions of standard-issue junk foods, but made to meet fat, salt, sugar and whole-grain standards, showed up immediately. Doritos, Cheetos, Cinnamon Toast Crunch cereal and Goldfish crackers all got back-to-school makeovers.

This, despite the fact that the companies that make all these foods acknowledge that selling to kids is something that should be limited, and many companies have implemented voluntary guidelines. PepsiCo, for example, has caps on calories per serving, saturated and trans fats, sodium and added sugars for any food it advertises to children and requires that it have one ingredient that’s a fruit, vegetable, whole-grain, low-fat dairy product, or nut (or alternatively, 2.5 grams of fiber per serving). The company doesn’t advertise to kids under 6 at all.

So what’s the big deal about extending those restrictions? Nestle told me that she attended a meeting put on by then-first lady Michelle Obama about food marketing to kids. “Industry people were there and they said, ‘Oh, wish we could stop marketing to children, but we have stockholders to please.’ ” I asked PepsiCo how they balanced their societal obligation to kids with their fiduciary obligation to shareholders, but they didn’t respond.

I support restricting advertising to kids, but reluctantly. The support is because, although the benefits are uncertain, and the impact will be small payback for the political capital expended, I think we should err on the side of protecting children. Although it’s parents’ responsibility to feed their kids healthfully, a stressed mom with about 68 gazillion other things to worry about could use a hand in battling marketing muscle. If restrictions can help even a few kids shape better habits and ward off weight gain, I want to be there for them.

The reluctance is because I believe that people — and parents — are powerful stakeholders in our food system, with agency to make changes. If you come here often you’ve heard me say it before: We’re not victims of our food system, but co-conspirators. We buy and eat the stuff that makes us fat and sick. I’m not opposed to the government saving us from ourselves, but I vastly prefer it if we do that job.

We need to walk back what Nestle calls “the normalization of junk,” and she believes the government can help reset norms. “Think of seat belts, think of cigarettes,” she told me, but I just can’t share her confidence. Norms are, almost by definition, grass-roots, and until we decide as a society to de-normalize junk, I don’t think government regulations will do more than nibble around the edges of the problem.

Which is why there’s one idea I will lend my full-throated support: loud, persistent condemnation of selling junk food to kids. It’s easy to talk about big, bad corporations that do it, but corporations are made of people. It’s people who decided to sell sugary cereal with cartoon characters. It’s people who figure out the best way to get kids to pester their parents at the grocery store. It’s people who decided to reformulate Flamin’ Hot Cheetos for schools. They should all be unemployable.

Calling out PepsiCo, and General Mills, and Kraft Heinz is easy and comfortable. Calling out people who make the decisions within those corporations is much harder, because it’s, well, personal. But it’s impossible for the companies to be at fault and the people not to be.

Selling junk to kids is, to my mind, a leading competitor for the most morally bankrupt job in the food system (and there’s stiff competition). If people — individual people — stopped doing it, there would be no need for long, wonky, wishy-washy columns about government intervention, and we could all go back to arguing about carbohydrate metabolism.

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