Is Fat Our Friend?

One day, not long after we got together, my husband opened the refrigerator after I had carried in some groceries. He leaned in to reach for something; stopped, arrested by something else he had spotted; frowned; and picked up a bottle of milk.

He put it on the counter. He called to me in my office. The conversation went something like this:

Him: “What is this?”
Me (puzzled at what seems self-evident): “It’s milk.”
Him: “It’s skim milk.”
Me (even more puzzled): “That’s what I said. It’s milk.”
Him (taking a deep breath): “Skim milk… is not milk.

This might be the time to mention that my husband comes from a farming family whose roots in Maine stretch back several centuries. His parents, their siblings and their parents were dairy farmers. The walls of one uncle’s house are studded with photographs of favorite cows, decades after they were sold.

These were not, let’s just say, people who demonized fat. They drank whole milk. They considered bread and butter an appropriate snack for children. They poached the spring’s first peas in cream.

As a health reporter, I thought this was insanity. After all, decades of research and public policy insisted that saturated fat was the enemy, the chief culprit responsible for the cardiovascular disease that is the leading killer in America. That my husband’s family didn’t seem to suffer those cardiovascular effects—that they lived long lives and were healthy and sturdy into old age—seemed to me a statistical quirk, a blip off the curve of what appeared a settled epidemiological trend.

But, a decade after that conversation, the science is swinging back to a reconsideration of what fat does—and more important, what it doesn’t do. How that happened turns out to be a fascinating story of the limitations of science and the influence of agribusiness, and of how hard it can be to change public policy on health.

The emerging understanding of fat’s influence, and in where the science went wrong, is captured in “Ending the War on Fat,” a new Time magazine cover story by Bryan Walsh that announces itself with an arresting close-up of an appetizing curl of butter. The story is behind a subscription paywall, but here’s what it says:

…the experiment was a failure. We cut the fat, but by almost every measure, Americans are sicker than ever. The prevalence of Type 2 diabetes increased 166% from 1980 to 2012. Nearly 1 in 10 American adults has the disease, costing the health care system $245 billion a year, and an estimated 86 million people are pre-diabetic. Deaths from heart disease have fallen — a fact that many experts attribute to better emergency care, less smoking and widespread use of cholesterol-controlling drugs like statins — but cardiovascular disease remains the country’s No. 1 killer. Even the increasing rates of exercise haven’t been able to keep us healthy. More than a third of the country is now obese, making the U.S. one of the fattest countries in an increasingly fat world. “Americans were told to cut back on fat to lose weight and prevent heart disease,” says Dr. David Ludwig, the director of the New Balance Foundation Obesity Prevention Center at Boston Children’s Hospital. “There’s an overwhelmingly strong case to be made for the opposite.”

This paradox—that eating something we have been persuaded is unhealthful might, in fact, have been healthier for us—is also explored in a new book, The Big Fat Surprise, by Nina Teicholz. And it’s been the professional life’s work of Gary Taubes, whose 2004 New York Times article “What If It’s All Been A Big Fat Lie?” led to two books and the founding of a research nonprofit. Taubes’ work is arguably responsible for igniting enthusiasm for low-carb (now “paleo” and “primal”) diets, whose popularity had foundered with the 2003 death of low-carb pioneer Dr. Robert Coleman Atkins.

What all these pieces of journalism have in common is a detailed exploration of how the original epidemiological assessments of diet’s effects were based on skewed data sets and incomplete historical evidence. Based on that evidence, the first-ever “Dietary Goals for the United States,” published in 1977, steered Americans away from food products containing saturated fat—meat, cheese, milk—and toward carbohydrates. They intended to encourage U.S. residents to eat more fruits and vegetables. What they accomplished, instead, was a vast expansion of the market for simple starch-based carbs, and for starch-based sweeteners that took the place of fat in industrial food production.

As an unintended consequence, they also opened the door to an enormous conversion of Midwestern farmland to corn to make corn syrup, while undermining the small-farm structure of the dairy industry, particularly in the Northeast. (Including my husband’s family; the cows are long gone, and the land is now planted for timber.)

The new science of fat is not just based on the experiential evidence that butter and cheese are tastier and more filling than crackers, producing pleasure and satiety and leading people to eat less. It’s also founded on sophisticated—and very disputed—understandings of the behavior of cholesterol, influenced by dietary fat, in the bloodstream. As the Time article suggests, evidence-based opinion about what people should eat may be suffering more internal disagreement than it has in decades.

While the case for fat isn’t settled, the emerging evidence makes me feel better about the whole milk, full-fat yogurt and small-producer cheese that have claimed space in my refrigerator since that conversation 10 years ago. Their presence in my kitchen doesn’t just represent deliciousness, or honor my husband’s heritage. It’s also in line with what Dr. Frank Hu of the Harvard School of Public Health tells Walsh: “We should be focusing on the quality of food, of real food.”

This story is part of National Geographic’s special eight-month Future of Food series.

R E Hunter
R E Hunter

It's not a limitation of science, but a failure of poorly-trained scientists and non-scientists trying to do science, combined with political/financial interests, some of which you alluded to. 

Population studies are a useful tool for finding correlations, from which causes and effects can be hypothesized, and those hypotheses tested in well-designed (sufficient size, double-blind, placebo-controlled) experiments. But until those experiments are conducted, reviewed, published, and duplicated no scientific conclusions can be drawn. Every scientist should know that correlation does not equal causation.

But in cases like the alleged harmful effects of saturated fat, population studies were done and hypotheses developed from them, but the rest of the steps were skipped, and the hypotheses taken as fact, with no evidence.

Years later, when the necessary experiments were actually conducted, the results were what we are seeing now, that saturated fat isn't bad at all. But by then, the dogma was so firmly established that it will take years to overcome.

This is the same thing that happened with Hormone Replacement Therapy, which killed thousands of women, by basing recommendations on flawed studies with no actual experimental evidence.


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