Why We Can't 'Nudge,' or Tax, Obesity Out of Existence

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Can we get our obesity problem under control? In part one of this series, we saw that common policy responses to our expanding waistlines have failed. Let's now consider why these interventions tend to yield such disappointing results.

The world is getting fatter, and public health experts don't know what to do about it. As we discussed in part one, a wide variety of interventions, everything from calorie labels to soda taxes, have failed to reduce obesity rates to any significant extent. Yet researchers working in this field can't bring themselves to give up on policies designed to “nudge” (or even coerce) consumers into making healthier food choices.

Here I want to examine why these interventions haven't worked and why many obesity experts seem to have such a hard time accepting this fact. Nobody knows how to rid the world of obesity, but the considerations below should at least point us in the right direction.

Plausible policies that don't work

It's undeniable that creating a calorie deficit through diet and exercise leads to weight loss. Given that observation as a starting point, prompting the public to eat less and exercise more should reduce obesity rates at the population level. The American Heart Association (AHA) study I cited in part one pointed to evidence from “behavioral economics” in support of this supposition, which “has demonstrated that humans are heavily influenced by default conditions in their environment.” [1] When individuals are made organ donors by default, the study authors continued, nearly 100 percent of them remain so, even when given the choice to opt out of their donor status. The argument goes that giving consumers healthier "default" food choices should have a similar effect.

If the fallacy isn't clear, let's spell it out: organ donation has no impact on someone's lifestyle. I suspect that donating their organs at the end of their days is merely a “sure, why not?” sort of decision for most people. Charging consumers more for food they enjoy, thereby making the “healthier” alternative the default choice, noticeably alters their options in a way they tend to resist. Watch this hilarious clip from the documentary Fat Head, and you'll see what I mean:



Many, though not all, obesity experts have difficulty seeing the equivocation between organ donation and food choices because they assume consumers can and should be manipulated into making smarter decisions. Consider the AHA commentary again:

"… [P]olluted air and water create negative defaults that damage health. Progress comes through removing the toxic agents, not by accepting them and urging people to react differently (eg, wear masks or boil water). … There is growing theoretical and scientific support for policies that intervene on environmental determinants of overeating. The implementation of some policies is facing resistance from the food and beverage industries."

If some foods are akin to “toxic agents,” then it only makes sense that they have to be removed from the environment. You can't expect the public to face such hazards alone, can you? You'd have to be a Coca-Cola lobbyist to deny the wisdom in such a policy!

Of course, this is all pure silliness because no food available in the local supermarket or a fast-food restaurant is remotely analogous to polluted air or water. The fact is, so-called “junk food” can be nutritious; a Big Mac can provide all the nutrients you should get out of a balanced meal and pack fewer calories than a salad. Let the cognitive dissonance wash over you.

So many obesity experts can't quit the idea of reshaping our "toxic" diets, even when their own research says they should, because they're surrounded by people who share their assumptions and therefore insulated from critical scrutiny. Economist Thomas Sowell outlined how academics can fall into this trap in his book Intellectuals and Society:

When the only external validation for an individual is what other individuals believe, everything depends on who those other individuals are. If they are simply people who are like-minded in general, then the consensus of the group about a new idea depends on what the group already believes in general—and says nothing about the empirical validity of that idea in the external world (p 7).”

In sum, obesity researchers have a collective case of confirmation bias. And like the rest of us, they have a difficult time changing their minds when confronted with evidence that they were wrong.

Why don't these policies work?

We have a reasonable explanation for why obesity researchers remain married to policies that yield little progress, but why do these interventions fail? There are almost certainly dozens of contributing factors. Among these is the fact that obesity is a complicated disease broadly controlled by “our underlying genetics, our metabolic condition, and our lifestyle choices,” as my colleague Dr. Chuck Dinerstein explained last year.

Policies that seek to alter our dietary choices can't address the fact that obese people often fail to lose weight even after cutting their intake of palatable foods. Moreover, addressing the influence of genetics and metabolism may require the input of a dietitian or physician who can help someone develop a more personalized weight-loss plan. Studies have shown that individualized advice of this sort yields more success than the standard “eat less, move more” recommendations.

Getting that input from healthcare providers can be challenging, though, since fat acceptance rhetoric is commonly used to pressure physicians into ignoring their patients' obesity. Healthcare providers best equipped to help individual patients manage their weight are being told not to intervene. Along the same lines, overweight Americans have consistently been told that they aren't even partially responsible for their size and that obesity doesn't carry serious health risks. No policy response can succeed in a population that has been conditioned to think of any dietary intervention as “oppressive.”

Bad dietary advice

Another possibility is that consumers are regularly bombarded with one-size-fits-all nutrition advice. The AHA, for example, “recommends aiming for a dietary pattern that achieves 5% to 6% of calories from saturated fat” in order to keep cholesterol down. But there is good evidence that this isn't the best approach for many of us. As the researchers behind a January 2019 clinical trial reported,

Those on a low-carbohydrate weight-loss diet who increase their percentage intake of dietary saturated fat may improve their overall lipid profile provided they focus on a high-quality diet and lower their intakes of both calories and refined carbohydrates.”

The point is not that carbs have made everybody fat; some people do quite well on high-carbohydrate diets. But nuances like these are lost on academic tinkerers who want to discourage global meat consumption with sin taxes; the optimal diet will probably vary among individuals. Policies that ignore such a possibility will leave a lot of people with unhelpful, even counterproductive, weight-control advice.

A final example before we wrap up: major medical journals continue to publish baseless epidemiological studies suggesting that low-calorie drinks are linked to weight gain and even cancer. Health reporters, always looking for an attention-grabbing story angle, dutifully repeat the dubious claims they read in university press releases. The result is that many consumers are encouraged to avoid harmless beverages that could cut a significant number of calories out of their diets.

Nobody has the perfect population-level solution to obesity. But a couple of things are clear at this point. Policy responses to obesity often work at cross-purposes and ignore pertinent influences on weight gain, including consumer preferences and the diverse nutritional needs of different people. Whatever the ultimate solution to obesity is, it has to account for all the relevant aspects of the problem. We'll never make much progress otherwise.


[1] “Regular” economists have blasted behavioral economics because it doesn't actually account for human behavior but takes credit for well-established ideas that preceded it.