If you’re old enough to remember the early 1990s, you may be familiar with SnackWell’s cookies. The popular, sugary snacks didn’t taste quite as good as regular cookies, but they made up for it with the virtuous glow produced by the words “low fat.”

Ann F. La Berge, a science and technology scholar, explains how we got to the point where we thought eating that sort of thing was a good idea.

One force contributing to the low-fat ideology was women’s dieting culture, which had begun in the late nineteenth century. By the 1920s, magazines targeting middle- and upper-class women regularly featured diet columns and recipes. In this context, the goal was losing weight to look good and fit into fashionable clothes rather than for health. Dieting usually meant counting calories, and since fat is more energy-rich than protein or carbohydrates, that usually meant cutting fat.

In the 1950s, medical researchers began broadcasting a different anti-fat message. At a time when meat-heavy diets were standard across much of the country and “vegetables” often meant something canned and soggy, coronary heart disease was the leading cause of death in the United States. A number of studies suggested a big problem was diets heavy on saturated fat and cholesterol. While the link wasn’t completely clear, many experts hoped reducing fat intake could help people at risk of heart problems.

Then the federal government got involved. In 1968, the Senate created a committee to look into hunger in America. Over the following nine years, committee members became convinced that a bigger problem was that Americans were eating too much and too poorly. In 1977, it published a set of dietary guidelines, suggesting that people reduce their fat intake, as well as increasing consumption of vegetables, fruits, whole grains, and lean protein.

“The diet-heart hypothesis remained a hypothesis, but, as if already proven, it became enshrined in federal public health policy and was promoted by health-care practitioners and the popular health media,” La Berge writes.

The food industry at first pushed back against the government recommendations, and succeeded in shifting some of the government guidelines—for example, getting “reduce meat consumption” changed to “choose meats and fish that will reduce saturated fat.” Soon, though, companies realized they could simply start marketing low-fat products, often adding more sugar to make up for the loss of flavor.

Between 1950 and 1998, as low-fat diets took hold, deaths from heart disease fell by an amazing fifty-three percent. But as it turns out, La Berge writes, this was a product of medical and surgical interventions. Incidence of heart disease actually remained steady.

By the early 2000s, many studies were undermining low-fat ideology. Health experts began recommending “good fats” like olive oil and avocados, and cautioning against too many carbs. Today, even the longstanding assumption that the saturated fat in whole milk is unhealthy is coming into question.

The lesson of the low-fat craze may be that eating plenty of fresh produce and avoiding overeating will always be better advice than whatever the latest study suggests.