A Salvo in the Calorie War

The calorie war is heating up. It’s actually been simmering for some time, sparked by an alarming obesity rate among young Americans and related spikes in diabetes and other health problems. Nobody really disputes this sorry trend anymore, but there is a lot of disagreement over what to do about it. Public health advocates are clamoring for everything from warning labels on junk food to aggressive television marketing campaigns, even for outright prohibitions. Just last week, the Obama administration entered the fray, calling for a total ban on candy and soda in the nation’s schools.

Some see the past tobacco war as the proper model for this public health campaign. Indeed, one idea that has gotten traction recently is another “sin tax”—this one a fat and sugar tax—to dissuade people from eating junk food. Yale University psychologist and diet expert Kelly Brownell, writing in the prestigious New England Journal of Medicine last spring, called for a penny-per-ounce tax on soda sweetened with sugar or corn syrup. Only such a tax, he believes—and not lectures about nutrition and exercise—will make people eat more sensibly, and what’s more, the revenue could be used to promote healthier foods and habits.

Not everyone agrees. Pricing strategies may well be a key to changing behavior, but others favor subsidies over punitive taxes, as a way to encourage people to eat fruits and vegetables and whole grains. The problem is that both these market approaches—taxes and subsidies—are founded on the belief that people make rational economic decisions: Make it cheaper and people will eat more of it, more expensive and people will eat less. But decades of behavioral economics research argues that consumers are not always so rational. And the two strategies have never been tested head to head, to see which one most effectively alters calorie consumption.

Until now. Leonard Epstein, a clinical psychologist at the University of Buffalo, decided to explore the persuasiveness of sin taxes and subsidies in the laboratory, and he did so in an innovative way. He and his colleagues turned their lab into a simulated grocery store, “stocked” with images of everything from bananas and whole wheat bread to Dr. Pepper and nachos. A group of volunteers—all mothers—were given laboratory “money” to shop for a week’s groceries for the family. Each food item was priced the same as groceries at a real grocery nearby, and each food came with basic nutritional information.

The mother-volunteers went shopping several times in the simulated grocery. First they shopped with the regular prices, but afterward the researchers imposed either taxes or subsidies on the foods. That is, they either raised the prices of unhealthy foods by 12.5 %, and then by 25%; or they discounted the price of healthy foods comparably. Then they watched what the mothers purchased.

It’s important to know how the scientists defined healthy and unhealthy foods. They used an index called calorie-for-nutrition value, of CFN, which simply means the number of calories one must eat to get the same nutritional payoff. So for example, nonfat cottage cheese has a very low CFN, because it is packed with nutrition but not with calories; chocolate chip cookies have a much higher CFN. The most sinful food in the store was commercial iced tea, with a whopping CFN equivalent to ten times that of chocolate chip cookies. The researchers also measured the energy density—basically calories—in every food.

Then they crunched all the data together, and the findings were striking. To put it bluntly, taxes worked and subsidies did not. Specifically, taxing unhealthy foods reduced overall calorie intake, while cutting the proportion of fat and carbs and upping the proportion of protein in a typical week’s groceries. By contrast, subsidizing the prices of healthy food increased overall calorie consumption without changing the nutritional value at all. Why? As reported on-line last week in the journal Psychological Science, it appears that mothers took the money they saved on subsidized fruits and vegetables and treated the family to some chips and soda pop. Taxes had basically the opposite effect, shifting spending from junk to healthier choices.

The scientists conclude that subsidizing broccoli and yogurt—as appealing as that idea might be to some—is unlikely to bring about the massive weight loss the nation now requires.

For more insights into the quirks of human nature, visit the “Full Frontal Psychology” blog at True/Slant. Excerpts from “We’re Only Human” appear regularly in the magazine Scientific American Mind. Wray Herbert’s book, On Second Thought: Outsmarting Your Mind’s Hard-Wired Habits, will be published by Crown in September.