How Fat Became Public Enemy No. 1, and Why It’s Enjoying a Comeback

For decades, we’ve been taught the same golden rule for maintaining a healthy weight: Simply burn more calories than you consume.

Therefore, being overweight, we’ve been told, is a personal flaw—a failure to follow the rules, or a result of weak willpower, laziness, or out-of-control gluttony.

But in recent years, a burgeoning number of scientists and journalists have come forward to suggest that the obesity crisis is caused by something far bigger than us: bad nutrition science, bad food policy, and chronic misinformation from the government and nutrition experts. In other words, it’s not (all) our fault.

In fact, the dietary advice we’ve been given for the past half century, they say, has created the perfect storm and near-ideal conditions for an obesity epidemic.

The Big, Fat Surprise: Fat Isn’t Bad for You

At the crux of issue, say advocates, is the demonization of fat that has been drilled into us since the 1970s.

It all started on Sept. 24, 1955, when then U.S. President Dwight Eisenhower suffered a moderate heart attack. Heart disease had been on the rise among middle-aged American men for years, and the president’s illness thrust the issue to the forefront.

As researchers scrambled to pinpoint a cause, charismatic and combative American physiologist Ancel Keys put forward a hypothesis: Saturated fat was the culprit, from foods like butter, red meat, eggs, and cheese. And it sounded completely logical: Eating fat makes you fat.

By the 1970s, Keys’s theory had taken hold among nutrition experts as the dominant paradigm, despite weak evidence and conflicting research that pointed to sugar, not fat, as the culprit.

As the war on fat took hold, dietary guidelines were changed and the food pyramid was introduced. Based on the idea that “a calorie is a calorie,” the pyramid advised minimizing all types of fat, which contain twice the calories of other major nutrients, such as carbohydrates. Instead, it recommended a diet centered around low-fat, high-carb foods (up to 11 servings of grain products like bread and pasta per day).

Meanwhile, food companies jumped on the marketing opportunity, stripping the fat out of products and promoting “healthy” options like low-fat cereal, crackers, cookies, and salad dressing. But they also knew that taking the fat out of food products meant losing flavor. The solution? Add sugar.

As saturated fat from foods like cheese and butter was put on the enemy list, they were replaced with products containing new “heart-healthy” fats, such as margarine made from chemically processed vegetable oils known as hydrogenated oils.

(These oils, which contain trans fats, are now facing widespread boycotts as we learn more about the dangers they pose. In 2015, the FDA determined that trans fats are “not generally recognized as safe and set a three-year time limit for their removal from all processed foods.)

The idea that fat and saturated fat are unhealthy has been so ingrained in our national conversation for so long that we tend to think of it more as ‘common sense’ than a specific hypothesis,” writes journalist Nina Teicholz in her fat-exonerating book “The Big Fat Surprise: Why Butter, Meat and Cheese Belong in a Healthy Diet.

But, like any of our beliefs about the links between diet and disease, this one, too, began as an idea, proposed by a group of researchers, with its origin fixed at a moment in time.”

Although much of the Western world adopted this new low-fat, calorie-counting approach, often replacing dietary fat with refined carbohydrates, we continued to get fatter. And fatter. Since the 1970s, obesity has increased by 200 percent, and diseases related to obesity and diabetes are currently responsible for the deaths of two out of every three Americans.

All Calories Are Not Equal

The old adages of “calories in, calories out” and “eat less and move more” simply haven’t worked for most people in the long term. There are many benefits to exercising more, but weight loss often isn’t one of them, since exercising tends to make us hungrier. And it’s nearly impossible to out-exercise a bad diet; to burn off one doughnut, you would need to walk briskly for almost an hour.

It’s also very challenging to count the exact number of calories you consume every day and compare it accurately to the amount you burn—just a minor miscalculation could add up to several pounds a year. And even when you do successfully restrict calories, your body works against you, fighting back as it goes into “starvation mode.”

The calorie theory also suggests that eating a handful of almonds is the same as drinking a can of Coke, because the calorie count is similar. Or that low-fat cookies and no-fat, high-sugar yogurts are healthy options.

New research has revealed the flaws in this way of thinking,” said Dr. David Ludwig, obesity expert and professor of pediatrics at Harvard Medical School, in his latest book “Always Hungry? Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently.”

Recent studies show that highly processed carbohydrates adversely affect metabolism and body weight in ways that can’t be explained by their calorie content alone. Conversely, nuts, olive oil, and dark chocolate—some of the most calorie-dense foods in existence—appear to prevent obesity, diabetes, and heart disease.”

Ludwig, dubbed the “obesity warrior” by Time magazine, has joined other doctors such as Robert Lustig, David Perlmutter, and Mark Hyman, and journalists like Teicholz and Gary Taubes, to introduce a new theory:

We don’t get fat because we eat fat or too many calories; we get fat because we eat sugar and processed carbohydrates, which are quickly digested and cause spikes in the hormone insulin. This reaction promotes fat storage in the body and sparks a vicious cycle of overeating as insulin spikes and plummets.

The new thinking goes, cut out the sugar and fast-digesting carbs (which your body treats as sugar), and you won’t get fat.

As anti-sugar crusader Lustig put it in his popular YouTube video “Sugar: The Bitter Truth: “You are not what you eat—you are what you do with what you eat.”

The advice to focus on calorie counting and low-fat diets to lose weight was based on weak science and has caused people great suffering while thwarting their sincere efforts to be healthy, says Hyman in his book “Eat Fat, Get Thin.”

We now know from the research that sugars and refined carbs are the true causes of obesity and heart disease—not fats, as we’ve been told,” he writes.

Our views on fat, thankfully, are shifting. Over the last five years, the scientific evidence has been mounting that high-fat diets outperform low-fat diets for weight loss and for reversing every single indicator of heart disease risk, including abnormal cholesterol, diabetes, hypertension, inflammation, and more.”

Retraining Your Fat Cells

Instead of counting calories, Ludwig suggests “retraining your fat cells” with high-quality foods, including healthy fats. Using the right types and combinations of foods (as well as managing stress, and getting good-quality sleep and enjoyable physical activity), fat cells can be reprogrammed to release their pent-up calories, he says.

Fat is a crucial part of our diet, he notes, because it so highly satiating. Avoiding it makes us overeat the wrong foods to appease cravings. Contrary to what we’ve been told, healthy fats from foods like nuts and cheese do not get stored in fat cells—unless they’re eaten with refined carbs and sugar.

Ludwig’s approach aims at shutting down the starvation response typical to most weight-loss diets by using nourishing whole foods that lower insulin levels and reduce inflammation. He advises eating a wide variety of nutrient-dense foods including full-fat dairy products like cheese and yogurt, healthy oils such as olive and avocado, and proteins like tofu, as well as nuts, vegetables, fruits, nuts, legumes, whole grains, and even dark chocolate.

He also suggests that each individual may have a different sensitivity to carbs, so it’s a good idea to test your body’s reactions to them. Start by cutting out all starches, added sugars, and artificial sweeteners for two weeks.

Then add back moderate amounts of whole grains and starchy vegetables. After that, reintroduce bread, potatoes, and other processed carbs, depending on your body’s ability to handle them. Do you instantly gain weight and feel sluggish when you eat white rice? Try brown rice or quinoa instead.

Fat’s Redemption

In recent years, some policymakers have started to back away from the focus on fat, as sugar takes its place as public enemy No. 1.

In 2015, the U.S. Office of Disease Prevention and Health Promotion removed limits on dietary cholesterol in its Dietary Guidelines and softened its view on reducing fat in its advice. Eggs, yolks included, were again touted as good for us. In recent years, the American Heart Association and other health organizations have backed away from the low-fat message and revised guidelines to focus more on the types of fat in foods and on the diet as a whole.

A 2015 study published by the British Medical Journal concluded that dietary advice on fat consumption—issued to millions of U.S. and U.K. citizens in 1977 and 1983 to cut coronary heart disease incidence—lacked any solid trial evidence to back it up and “should not have been introduced,” researchers concluded.

A nonprofit led by Taubes, a science journalist at the forefront of the anti-sugar, fat-friendly hypothesis, was created in 2014 to address this research problem. The aim of the organization, Nutrition Science Initiative (NuSI), is to throw out everything we know about nutrition science and start from scratch.

With the help of generous funding, NuSI aims to conduct the type of long-term, independent, and ambitious studies that nutrition research rarely gets the money for to find reliable answers to our big nutrition questions. Taubes also invited naysayers—proponents of the low-fat, calorie balance approach—to do some of the research.

While many scientists and nutritionists start questioning the supposed dangers of saturated fat, the progress is slow and policymakers are treading carefully—lest they make another big, fat nutrition mistake.


March 29, 2023


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