We should never have told people to stop eating fat
That national dietary shift from fat towards sugar came about at least in part because of a major 1967 review of dietary science. Those historical documents reveal that a food industry group called the Sugar Research Foundation (SRF) paid three Harvard researchers $6,500 (about $50,000 today) to discount research that increasingly showed links between sugar and heart disease and to point the blame at fat instead. The industry group selected the data the Harvard scientists used for the review and suggested the research they include. Their final paper, published in the New England Journal of Medicine, set the US diet on a new course.
"The documents leave little doubt that the intent of the industry-funded review was to reach a foregone conclusion," Marion Nestle, Paulette Goddard Professor of Nutrition, Food Studies, and Public Health at New York University, wrote in a commentary published alongside the new analysis.
These revelations are new, but for years now, scientists have been wondering whether we got fat all wrong in the first place.
A major 2015 meta-analysis argued that there was never enough evidence to curb our consumption of fatty foods in the first place. Documentaries like "Fed Up" made the argument that sugar is a bigger problem than fat in today's obesity and diabetes epidemic, and another well-cited recent study found that saturated fat did not seem to be as bad for heart health as guidelines made it out to be.
Dietary guidelines in the US still say that we should restrict saturated fat to under 10% of daily caloric intake and that adults should not get more than 20% to 35% of their daily calories from fats.
The American Heart Association is even stricter, recommending limiting saturated fat to 5% to 6% of daily caloric intake - though those recommendations are based on what the evidence suggests is best for adults already at risk of heart disease, says Dr. Alice H. Lichtenstein, the director of the Cardiovascular Nutrition Laboratory at Tufts and a member of the nutrition committee at the AHA.
Guidelines restricting fat consumption to present-day levels went into effect in the US in 1977 and in the UK in 1983. But that 2015 meta-analysis of those guidelines, published in the BMJ journal Open Heart, comes to the conclusion that there was not evidence to support them in the first place.
After looking at the research on fat and sugar consumption that existed at the time, the authors of that analysis concluded that the "dietary advice not merely needs review; it should not have been introduced."
At the time, we didn't know that the research that ostensibly provided support for those guidelines had been tainted by industry funding.
The evidence for limiting fat when the guidelines were introduced
The authors of the Open Heart study say they wanted to understand the evidence used to establish present-day guidelines for dietary fat consumption. In particular, they wanted to see whether the dietary guidelines that affected 276 million people in the US and UK at the time had been tested using randomized controlled trials, which are considered the gold standard and most informative test for any clinical decision.
But when the low-fat guidelines were put into place more than 30 years ago, neither the UK nor the US cited any of the randomized controlled studies available at the time. And even if the two countries looked at them, it would have been hard to use them as evidence that dietary fat was a problem.
The authors of the 2015 study found eight randomized trials that would have been available to policymakers, which would have included 2,467 men and no women. Testing various dietary changes involving fat had no impact on the subjects' likelihood of death, either from heart disease or any other cause.
So hundreds of millions of people were given dietary guidelines that were arguably not supported by the evidence.
"I pleaded in my report and will plead again orally here for more research on the problem before we make announcements to the American public," Olson said.
But McGovern replied, "Senators don't have the luxury that the research scientist does of waiting until every last shred of evidence is in."
How cutting fat could have been bad for our health
Recently, an increasing amount of research says saturated fats - those in butter and cheese - just aren't as bad for you or your heart as we thought.
Many researchers have said that focus on fat led people to consume carbohydrates instead, from refined sugar in particular, which seems to have been the intent of the SRF-funded 1967 research. When those researchers shared drafts of their work with then-SRF vice president John Hickson, he replied: "Let me assure you this is quite what we had in mind and we look forward to its appearance in print."
Now, researchers say all that sugar consumption has led to a serious increase in the diabetes rate. When a low-fat diet was tested against a low-carbohydrate diet - as long as both were low in calories overall - the low-carb was much more beneficial, the researchers showed. People on the low-carb diet lost abdominal fat and body mass, had improved glucose tolerance, better cholesterol, and less inflammation. All of those measurements got worse on the low-fat diet, in which fat was replaced with carbs.
When the low-fat craze swept society, people didn't necessarily consume fewer calories by steering clear of fat - they just ate trans fats instead of saturated fat, which turned out to be much worse for health, or they consumed carbs, especially sugars and processed "low-fat" snacks, which may also be much worse for us.
Throw out the guidelines and eat endless cheeseburgers?
Should we rejoice and celebrate that, as food writer Mark Bittman writes, butter is back?
Not entirely.
First of all, Lichtenstein says, no one now - not the AHA or national health guidelines - is promoting a "low fat" diet anymore. She says health experts agree that directing people toward low-fat diets caused them to consume carbs and sugar "with abandon," which clearly had negative consequences. Now, she says, health experts promote a moderate fat diet, still getting about 30% of calories from fat but replacing saturated fats with healthier fats when possible, like those from vegetable oils. We realized that going low fat was bad even before we knew those ideas were funded by pro-sugar groups.
Further, she says that some of the reviews that seem to vindicate saturated fat are too broad and incorporate too many different types of studies - some that cut saturated fat when it might be replaced by carbs (not healthy), others in which healthier fats are consumed instead of saturated fats. She says that if the focus is on consuming "healthy fat" instead of saturated fat, those health benefits are clear.
As for the history of nutritional guidelines, randomized controlled trials may not have provided evidence telling us to cut fat out of our diets, but as cardiologist Rahul Bahl points out in an editorial published along with the 2015 study in Open Heart, that doesn't mean there's no evidence at all.
As the American Heart Association notes, eating more saturated fat is associated with a rise in cholesterol, and while not all cholesterol is bad, higher levels of one type of cholesterol from saturated fat are associated with a greater risk of heart disease and stroke.
Others argue that those associations don't mean the link between saturated fat and heart disease has been proved.
Normally, he says, those guidelines are made based on evidence that is observed in large populations over time. He says one example occurred because of political changes in Eastern Europe in the 1990s, when large populations started consuming more healthy fat from vegetable oils, which was associated with improved heart health.
He told Business Insider, however, that he does think it is worth revisiting nutritional guidelines to incorporate new evidence and to take a more thorough look at carbohydrates, especially sugar.
"There is certainly a strong argument that an overreliance in public health on saturated fat as the main dietary villain for cardiovascular disease has distracted from the risks posed by other nutrients," he wrote in the editorial.
That doesn't mean it's the end of the story. "I think the real relationships between all these nutrients and health outcomes is probably more complicated then we have examined in most studies so far," he told Business Insider.
For now, though, several things are certain: First, the low-fat guidelines jumped the gun. For most people, it is long past time to give fats - especially healthy ones - a prominent place on your plate. Second, the newly published JAMA historical analysis provides even more of a reason to make sure that industry groups aren't funding the research that we use to guide the way we eat.
As the New York Times revealed in 2015, Coca-Cola provided millions of dollars to support research that implied sugary drinks weren't necessarily linked to growing obesity rates. As Nestle points out in her commentary, other companies do the same. Candy companies promoted studies showing that kids who eat candy have healthier body weights.
"Today, it is almost impossible to keep up with the range of food companies sponsoring research-from makers of the most highly processed foods, drinks, and supplements to producers of dairy foods, meats, fruits, and nuts-typically yielding results favorable to the sponsor's interests," Nestle writes. "Food company sponsorship, whether or not intentionally manipulative, undermines public trust in nutrition science, contributes to public confusion about what to eat, and compromises Dietary Guidelines in ways that are not in the best interest of public health."