Encouraging consumers to reduce the fat or sugar in  their diets has done little to reduce obesity rates. Why is that?

In the Fight Against Obesity, the Real Enemy Is Oversimplification

All over America, public health campaigners are urging their fellow citizens — especially children — to cut back on sugary drinks and to eat foods with less added sugar. Cities like Berkeley and Philadelphia have levied taxes on soda, the Food and Drug Administration will soon require food labels to include information on added sugars, and schools around the nation are banishing soda from cafeterias and vending machines.

The sugar industry worked overtime to ensure that sugar was a welcome part of any diet. Today, it’s Dietary Enemy No. 1. Either way, Americans have gotten fatter.

Sugar does make a terrific dietary villain. It’s easy to identify, it has no redeeming nutritional value, and it’s backed by large companies that have spent billions both advertising it and underwriting scientific research that gave sugar a clean bill of health for decades. And the eat-less-sugar message is getting through. Since 1999, Americans have cut sugar consumption by 14 percent. Much of that reduction has come from soda, which adults and children are drinking less of.

There’s just one problem: We’re not getting any thinner. The most recent data from the Centers for Disease Control and Prevention, from 2014, show an 8 percent increase in obesity in just two years. So an ingredient is identified as a problem, people eat less of it, and nothing really changes.

If that pattern sounds familiar, perhaps you remember that sugar wasn’t always Dietary Enemy No. 1.

Based on research done in the 1950s, 60s, and 70s, the virtues of cutting back on fat were a bedrock part of the nutritional canon. In 1968, the American Heart Association issued eight dietary guidelines, and the only specific recommendations were to reduce animal fat, replace saturated fat with polyunsaturated fat, and reduce cholesterol.  All the others were general advice to maintain “ideal” body weight, to develop “sound food habits,” and to start doing so early in life. The first two versions of the Dietary Guidelines for Americans (1980 and 1985) likewise said, “Avoid too much fat, saturated fat, and cholesterol.”  (They also said “Avoid too much sugar,” but the emphasis there was on dental health.)

As a result, Americans did consume a bit less fat. Our intake peaked in 1986, at 43 percent of calories, and decreased gradually to a low of 38 percent in 1997. And yet, over that same period, we got much, much fatter, with the obesity rate going from 22.9 percent of the population to 30.5 percent. By 2010, the last year for which USDA data are available, we were back to 43 percent of calories from fat.

The data on sugar are strikingly similar. According to the United States Department of Agriculture, sugar consumption is down from 427 calories a day in 1999 to to 366 in 2014. In that time, the obesity has gone from 30.5 percent to 37.7 percent. Not quite as big a jump as during the less-fat days, but awfully close.

Still, these two pieces of advice — neither of which seems to have had much impact on public health — are the stuff of an acrimonious battle in the nutrition community, with some of the staunchest advocates for reducing sugar intake being the harshest critics of fat reduction advice. Take Robert Lustig, a pediatric endocrinologist and professor at the University of California, San Francisco. When it comes to the importance of eating less sugar, he wrote the book: “Fat Chance: Beating the Odds Against Sugar, Processed Food, Obesity, and Disease.” He argues that a fundamental misreading of nutrition research of the 1950s and 60s led to the “eat less fat” recommendation and that “the low-fat diet is what got us into this mess” of obesity and disease. Meanwhile, sugar, which Lustig claims is “toxic” in the quantities Americans eat it, sneaked into product after product.

It’s no paradox that sugar consumption is down but obesity isn’t, Lustig wrote in an email: “Sugar accounts for only about 10 percent of weight gain,” so small reductions aren’t “likely to make much of a difference in weight or obesity rates.” Instead, the problem lies in the way we metabolize one particular sugar — fructose, which makes up about half of the two major sweeteners, table sugar and high-fructose corn syrup.

Fructose is the “driver of metabolic dysfunction, unrelated to its calories and unrelated to weight gain,” Lustig says. It wreaks havoc with our endocrine system, raising the risks of heart disease and diabetes.

While it’s true that new diabetes diagnoses have dropped since 2009, in tandem with the decline in sugar consumption, there’s not widespread agreement on Lustig’s take on fructose. Luc Tappy, a professor of physiology at the University of Lausanne in Switzerland and a member of the government-sponsored committees crafting developing dietary recommendations both there and in France, calls the metabolic impact of fructose an “open question.”

Regardless, pretty much everyone agrees that eating less sugar is a good idea. You don’t have to believe in the metabolic dysfunction theory to think it’s smart to curb your intake of nutrition-free calories.

Fat is more complicated. According to Alice Lichtenstein, vice chair of the 2015 Dietary Guidelines Advisory Committee, there’s general agreement that mono- and polyunsaturated fats are healthful and trans fats are not. Saturated fat, though, has made headlines as scientists re-evaluate its role in disease. Even though the “majority of the data” supports limiting it, says Lichtenstein, the issue is “controversial and confusing.”

But the two pieces of advice have something in common, something important enough to undermine the effectiveness of both, regardless of the consensus or lack of it: They’re both focused on just one component of our diet. Eating less sugar, in particular, may be necessary, but it is certainly not sufficient. Yet because everyone agrees on it, that advice dominates the nutritional agenda, drowning out more nuanced or broad-spectrum advice.

“Partitioning macronutrients into good and bad guys is a big mistake,” Tappy says, because nutrition is complicated. The effect of those macronutrients “varies according to food consumed,” and you can have an excellent diet that includes them or a lousy diet that doesn’t.

Despite reductions in both sugar and fat consumption, obesity rates have continued to climb.

Look at any diet that has gotten traction in the last 30 years, and it’s likely to be about just one thing. It’s fat. It’s carbs. It’s gluten. It’s meat.  Although the diets generally include recommendations about overall patterns as well, the one-thing advice dominates: All you have to do is not eat that, and you’ll be fine. The fatal flaw in such advice is that it’s much too easy to do that one thing and still eat badly. “People don’t listen to advice unless they can follow that advice and still eat what they want,” says Michael Jacobson, co-founder and president of the Center for Science in the Public Interest, a consumer advocacy organization that has campaigned for reducing sugar consumption through measures like soda taxes and removing sugary beverages from schools.

Marion Nestle, a professor of nutrition, food studies, and public health at New York University and the author, most recently, of “Soda Politics: Taking On Big Soda (and Winning),” calls it the “Snackwells Phenomenon.”

Nestle edited the 1988 Surgeon General’s report, which concluded that dietary fat was the most serious problem in the food supply. The assumption behind that recommendation, she explains, was that “If you cut down on meat and dairy, most of your diet would be fruits, vegetables, and whole grains.” She didn’t bargain for Snackwells, a Nabisco line of low- to no-fat cookies introduced in 1992, to help people follow the eat-less-fat advice.  “People lined up to buy them,” she says. “I was stunned.”  The mistake — and Nestle admits it was a mistake — wasn’t the recommendation to eat less fat. It was a failure to anticipate what people would eat instead, and the lengths the food industry would go to help them follow the guidelines of the day without actually eating more healthfully.

From 1989 to 1995, the percentage of new food products with a low-fat or no-fat claim on the label nearly tripled, from 9.2 to over 25 percent.

Part of the problem, Nestle says, is that the lower-fat versions had about the same number of calories as the full-fat versions, but the “low-fat” label imbued them with an air of healthfulness, and people thought they could eat them with impunity. “Any label like that on a food product makes people think it doesn’t have calories. ‘Organic’ labels make people think it has fewer calories.”

Food manufacturers, she goes on, “are in the business of selling food. They’re not social services agencies. Part of their business is to take advantage of the current dietary advice.”

The low-fat trend wasn’t current for very long.  After a couple of years dominating grocery shelves, the number of new products with those claims dropped as fast as they had risen.  From 2001 on, they went down to 13 percent or less.

Some of the focus has shifted to sugar. Unilever is reformulating its bottled teas, General Mills its cereals, and Yoplait its yogurts.  While some of the reformulated foods are somewhat lower in calories and have been genuinely improved, the silliness of focusing on one particular ingredient is also on display. Sweetgreen, the salad-centric restaurant chain, for example announced in May that it was taking Sriracha, the popular brand of hot sauce, off the menu. Why? “The second ingredient in Sriracha is sugar,” the company said in a statement.  With only one gram of sugar per teaspoon, it’s unlikely that Sriracha is doing us harm.

The larger question is whether these changes, some meaningful and some not, will have an impact on obesity and its attendant diseases, or whether American consumers will simply find a way to follow the advice but eat unhealthily anyway. If we opt for vegetables, that’ll be a win for the ages. But if we go with French fries (Hey! No sugar, and didn’t I read that fat wasn’t so bad after all?) and cheeseburgers (ditto), we’re not making much progress.

In the most recent set of dietary guidelines, the U.S. government suggested that previous emphasis on individual dietary components may have been a mistake.

In the most recent set of dietary guidelines, the U.S. government suggested that previous emphasis on individual dietary components may have been a mistake.

This past January, in its latest five-year updating of the Dietary Guidelines for Americans, the government floated an explanation for that lack of progress. “Previous editions of the Dietary Guidelines focused primarily on individual dietary components such as food groups and nutrients,” the executive summary reads. “However, people do not eat food groups and nutrients in isolation but rather in combination, and the totality of the diet forms an overall eating pattern.”

Lichtenstein, of the Dietary Guidelines Advisory Committee, sees one-thingness as a problem, and emphasizes that we have to look at the patterns and not just the components. Focus on one particular food group or nutrient, and “people figure out how to eat around it,” she says. “You see it in low-carb. You see it in gluten-free. You see it in low-fat. You see it in the singular focus on sugar.”

Unfortunately, diet advice that focuses on patterns doesn’t seem to get traction. Michael Pollan’s “Eat food. Not too much. Mostly plants” may be the single best example of good advice American eaters just won’t take. Fat intake dipped in the less-fat era. Sugar intake is dipping now. But when it comes to vegetables, our intake remains stubbornly low.

In short, the advice we follow is ineffective and the advice that would be effective isn’t followed. “To a certain extent they’re mutually exclusive,” says Lichtenstein. Where does that leave the legions of doctors, scientists, and health professionals who go to work every day in the hope of helping us conquer obesity?

In a tough spot, say experts like Jacobson, of the Center for Science in the Public Interest. “We’re not going to see declines in adult obesity for decades,” he says. “We have this cohort of people who are 20 and up that has to wash out.”

By “wash out,” he means, of course, “die.” And while he’s clearly not giving up on adults — not after 45 years of doing battle — he’s not the only one who thinks our current food environment makes it prohibitively difficult for grown-ups to change their habits.

“I think education without environmental change is a lost cause,” says Barry Popkin, a professor of nutrition at University of North Carolina at Chapel Hill. “The people who are already educated are the people who follow diet advice. They pay attention, read the paper, and have the money to make changes.” Not so much in low-income and minority communities, where obesity takes its highest toll.

For health to improve among the most vulnerable, Popkin believes that prices have to change. “We need to change the culture of eating,” he says, “but we have very little real food and people can’t afford it.  When unhealthy is cheaper than healthy, that’s what happens.” He’s working with countries around the world to promote taxes and market controls that could change the picture.

Nestle and Lichtenstein agree that the food environment stacks the deck against people trying to eat better. “It’s roughly $12 billion a year for ads for food products, restaurants, alcohol,” Nestle says of the food industry, “and for every dollar spent through ad agencies, there’s another two dollars spent on marketing in other ways. People are bombarded.”

Lichtenstein is focused on how easy it is to make unhealthful choices. “When you go to a restaurant, you don’t get whole-grain bread on the table. When you order an entrée, rarely is there a reasonable-sized serving of a vegetable. For the most part, people will eat and drink what’s put in front of them.  We have to work to make the default option the healthier option.”

The bickering over who’s right, the anti-fat camp or the anti-sugar camp, seems beside the point when there’s so little confidence that either strategy will have a meaningful effect on public health.  The fat and the sugar, they’re the deck chairs. The cheap, irresistible, high-calorie, low-cost food, backed with billions in marketing money — that’s the iceberg.

But there is one potential bright spot.

Marlene Schwartz, director of the Rudd Center for Food Policy & Obesity at the University of Connecticut, is also skeptical that enough adults can lose weight to produce a shift in population-level data.  But she sees hope in the next generation: “My prediction is that in the next five years you’re going to see changes in children.”

Those changes may already be happening.  Obesity in children is holding steady, but that’s because it’s increasing among teenagers; among the very young, ages 2 to 5, it’s going down. Kids are also drinking less soda — their consumption is going down faster than those of adults.  More importantly, children are being exposed to a variety of programs that address their diet as a whole (as well as their exercise habits), mostly at school. Lunches, snacks, and vending machines are being overhauled. Some schools are planting gardens. And kids are increasingly being taught about cooking and nutrition.

A prime mover in the undertaking is First Lady Michelle Obama’s Let’s Move initiative, which Executive Director Deb Eschmeyer describes as a “multidimensional” effort across the entire spectrum of children’s experience — not just more exercise, but “healthier schools, healthier day care, healthier convenience stores.” Let’s Move is the opposite of one-thing; it’s an effort to transform environments. That is hard to do with adults, Schwartz says, but “it’s a lot easier to be paternalistic when we talk about children.”

“Kids who are now in school will have 13 or 14 years of being exposed every day to healthy lunches and snacks,” she says. “This generation will have a better diet than the generation before it.”

Eschmeyer acknowledges that childhood obesity is holding steady for now, but she’s in it for the long haul. “It’s going to take patience and persistence,” she says. “We won’t see the real impact for many years to come.”

In the meantime, if you’re an adult and you don’t want to “wash out,” what should you do? There is good advice out there, says Nestle, and we’ve all heard it. One more time: “Eat food. Not too much. Mostly plants.”

Tamar Haspel is a journalist who has been writing about food and science for nearly two decades. She writes the James Beard Award-winning Washington Post column Unearthed, which covers food supply issues, and contributes to National Geographic, Fortune, and Cooking Light.