For years, dietary advice held that we should limit our salt, fat, and cholesterol intake. There’s a big problem with that, though: Salt, fat, and cholesterol all to varying degrees either make food taste good, or are found naturally in foods that people enjoy eating. If we’re trying to avoid them, and if the life of an ascetic doesn’t appeal to us, what shall we eat?

The answer was sugar. Sugar also tastes good. For more than a generation, Americans in particular have substituted sugar and other carbohydrates for the fats that they used to consume. They’ve also upped their calorie intake, again largely from sugar. The downsides here seemed few, because dental cavities are not life threatening, and because, although sugary foods may be low in vitamins and other nutrients, most Americans were getting those nutrients elsewhere, making deficiencies relatively rare.

Now, though, scientific opinion has shifted, prompted by two bodies of evidence. First, there has been an epidemic of obesity that seems increasingly to have been the fault of excess sugar consumption. And second, the dietary harms from salt, fat, and cholesterol seem to have been much less than initially feared. Fat does not make people fat — but sugar does, says the new thinking. Sugar also may be to blame for diabetes, heart disease, and a host of other maladies.

The role of government nutrition guidelines looms large in these matters, because these guidelines shape institutional food practices in places like schools, hospitals, and prisons, and because the guidelines shape public health campaigns for the rest of us. Has sugar been making us fat? And if so, has the federal government had a hand in it? And what’s to be done about it?

Joining us to discuss this month are noted science author Gary Taubes, whose lead essay reviews the state of the science and recaps the recent history of U.S. federal government dietary advice. Responding to him are obesity researcher Stephan Guyenet, Professor Yoni Freedhoff of the University of Ottawa, and Professor Terence Kealey of the University of Buckingham. We welcome your comments to their posts and look forward to a stimulating discussion.

Lead Essay

  • Gary Taubes tells a tale of unintended consequences: When the U.S. Department of Agriculture issued the first federal dietary guidelines, it may have hoped to steer Americans away from excess fat and toward a diet of whole fruits and vegetables. But this did not happen: Overwhelmingly, Americans turned to processed, sugary, and high-carbohydrate foods instead. The result was an epidemic of obesity. Meanwhile, dietary science continued to evolve. The case against fat weakened significantly, while the case against sugar strengthened. Yet scientists do not deal in certainties; their findings come with varying degrees of confidence, a state of affairs that public policy has difficulty reflecting.

Response Essays

  • Stephan Guyenet says Americans can’t blame government nutrition advice for their overconsumption of sugar. Dietary guidelines issued in 1980 didn’t recommend substituting sugars for fats; they recommended decreasing consumption of both. Americans, however, started eating more sugar anyway. Nor is it clear that sugar is to blame for obesity, because American sugar consumption peaked in 1999 and has declined ever since. Meanwhile, obesity has continued on a steady upward trend. Sugar is one part of a larger picture that explains American obesity, diabetes, and heart disease; it is not the sole culprit.

  • Yoni Freedhoff says that the public policy debate about nutrition would benefit from a practical, clinical perspective. American’s eating habits have changed a lot since 1977, and while sugar is a part of that change, it’s only one part among many. Americans eat more meals outside the home. They eat more pre-packaged ready-to-eat meals. They eat larger portions. And they eat many more calories altogether. The case against fat in the 1970s and 1980s was certainly flawed, but those flaws can’t be blamed for Americans’ poor dietary choices in the meantime, and, what’s worse, today’s critics of sugar may be replicating some of the same mistakes.

  • Terence Kealey praises Gary Taubes for being willing to submit his nutritional theories to empirical testing. Rather than trading on influence and suspicion, Taubes has articulated a hypothesis, namely that sugar is to blame for metabolic syndrome, and he has called for further research in the area: not panic, not grandstanding, but the same sort of testing that brought us to become skeptical of earlier conclusions that have now been rejected. If the sugar hypothesis is correct, it will stand the testing. If not, it deserves to be rejected. Public health and government guidelines should wait and see, and follow the research.

Related at Cato

Policy Analysis: Menu Mandates and Obesity: A Futile Effort, Aaron Yelowitz, April 13, 2016

Cato Unbound: Can Public Policy Stop Obesity? January 2015

Cato Unbound: Slippery Slopes and the New Paternalism, April 2010

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