隨著脂肪論戰的發起，膳食指南改變了，食物金字塔被引入。基於「1卡熱量 = 1卡熱量」的想法，食物金字塔建議將所有脂肪攝入降到最低，因爲比起碳水化合物等其它主要營養物質，脂肪含兩倍的熱量。這種方法建議人們以低脂肪、高碳水化合物食物為主，每天可食用11份穀類食物，如麵包和麵食。
記者Nina Teicholz在她關於脂肪的書《 一個關於脂肪的大驚喜：為什麼黃油、肉和奶酪屬於健康飲食》中寫道：「長久以來，脂肪和飽和脂肪不健康的觀點在我們的國民討論中已經根深蒂固，我們傾向於將它認為是『常識』，而非一個具體假設。 」
哈佛大學醫學院肥胖專家、兒科教授David Ludwig博士在新書《總覺得餓？征服慾望、重煉脂肪細胞、永久減肥（Always Hungry? Conquer Cravings, Retrain Your Fat Cells, and Lose Weight Permanently）》 中說：「最近的研究表明，高度加工的碳水化合物對人體代謝和體重都有不利影響，這種影響無法單獨以卡路里含量解釋。相反，堅果、橄欖油和黑巧克力，一些熱量密度高的食物卻似乎可以預防肥胖、糖尿病和心臟病。」
Ludwig博士被時代雜誌評為「肥胖鬥士」，他與其他醫生如Robert Lustig，David Perlmutter和Mark Hyman，以及Teicholz和Gary Taubes等記者一起，介紹了一種新的理論：我們變胖不是因爲吃脂肪或熱量過多的緣故，是因爲吃糖和精製碳水化合物，它們被快速消化並引起胰島素釋放。這種反應促進身體中的脂肪儲存，並因爲胰島素水平的驟然升高和下降，而引發暴飲暴食的惡性循環。
反糖十字軍的Lustig，在他受歡迎的YouTube視頻《糖：苦澀的真相（Sugar: The Bitter Truth）》中說：「並非你吃了什麼，你就多了些什麼。重點是你吃的食物在身體裡發生了怎樣的變化。 」
Hyman在《吃脂肪變瘦（Eat Fat, Get Thin）》一書中指出，專注於熱量計算和低脂肪飲食來減肥的建議，實際上是基於薄弱的科學知識。它讓人們在減重過程中受了不少罪，而且感到十分挫敗。
2014年，支持抗糖、脂肪友好假說的前沿科學記者Taubes領導創立了一個非營利組織Nutrition Science Initiative（NuSI），以期解決這一研究問題。這一組織的目標是拋開我們對營養科學所知的一切，從頭開始。
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.Fat is a crucial part of our diet because it so highly satiating. (Benjamin Chasteen/The Epoch Times)
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, salmon, and lamb, 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.
Sheet-pan salmon, a three-in-one meal. (Caroline Chambers)
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 mistake.