You've probably heard that fat is bad for you. Food manufacturers market and sell fat-free and low-fat products. Restaurants trim fat off meat. And when folks like Dr. Robert Atkins said we should eat more fat and less cereal, they were shouted down by a legion of nutritional experts.
Back in 1973, Atkins was called in front of Congress to defend his diet. One senator told Atkins he had "impugned the reputations" of the doctors who preached that the best way to lose weight was to avoid fatty foods. The American Medical Association attacked Atkins's low-carb diet as a ''bizarre regimen."
The medical establishment went all-out against fat a decade later. In 1985 the National Heart, Lung, and Blood Institute launched a successful national program aimed at reducing cholesterol, which included an effort to get people to lower their saturated fat intake. The notion that people should eat less fat to stay healthy was so seemingly intuitive that it caught on.
Today fat is still looked down upon. The governments of both the United States and Great Britain encourage their citizens to eat less saturated fat. "Consumer Reports" labels saturated fats as "bad." They're hardly alone. Mainstream health experts seldom go on TV and tell people to eat more fat. Food manufacturers never slap "Now with Extra Fat!" on food packaging. There is no McDonald's McFat Burger. The First Lady has yet to launch a "Let's Eat More Fat!" campaign.
In the refrigerator of justice, fat is one of the bad guys.
Or is it?
A funny thing happened on the way to lowering America's cholesterol. America's high blood cholesterol and consumption of saturated and total fats decreased while its obesity continued to rise.
America is eating less fat, and it's getting fatter.
How can that be?
Total fat in any food, or in the diet, should be ignored. One should focus on eating more healthy foods.
Dariush Mozaffarian, Harvard School of Public Health
Let's Take Another Look at Fats
When health experts rallied against fat in the 1980s, they were working with the data they had. The case against saturated fat in particular was that it had far more calories than other food groups and it raised LDL, the bad cholesterol.
New research is available, and it says that if one removes saturated fat from one's diet, it needs to be replaced with something healthier. For a long time, we didn't make a healthy swap. Many of us still haven't.
Today, there is a consensus that polyunsaturated fats and monounsaturated fats are healthy. (See sidebar for details.) Saturated fats? The conventional wisdom says they're harmful, but that tells only part of the story.
In 2010 Patty Siri-Tarino, an associate staff scientist with Children's Hospital Oakland Research Institute, published a meta-analysis of the association between dietary saturated fat and risk of coronary heart disease, stroke and cardiovascular disease. The analysis looked at 21 separate epidemiological studies that met certain guidelines.
The conclusion: There is insufficient evidence to conclude that saturated fat raises the risk for stroke, coronary heart and cardiovascular disease. The researchers say more study is necessary to determine whether there are associations between the aforementioned health risks and saturated fat in specific age and sex subgroups.
"Very likely, the reason for the lack of association of saturated fat with cardiovascular disease was that people were replacing their saturated fat with carbohydrates," Siri-Tarino said. "When you increase carbohydrate in the diet, it can lead to a different problem. It can induce an atherogenic dyslipidemia. You think you're doing something healthy by decreasing saturated fat, but replacing it with carbohydrates, especially refined and processed carbs, is not going to help you."
Atherogenic dyslipidemia, according to the National Institutes of Health, comprises a triad of increased blood concentrations of small dense low-density lipoprotein particles, decreased high-density lipoprotein particles and increased triglycerides. It is a feature of obesity and a risk factor for cardiovascular disease.
Studies like this one shed light on the fact that public health experts' efforts to lower saturated fats and bad cholesterol to reduce heart disease may have led to an increase in atherogenic dyslipidemia, which is a risk factor for heart disease. It's possible that when we reduced saturated fats in our diets we replaced them with processed carbohydrates and didn't do ourselves any favors.
Replacing saturated fat with polyunsaturated fat is beneficial, according to research studies, although not all of them. What's evident is: there is still much to be learned about fat.
A 2010 study by the Harvard School of Public Health using randomized clinical trials found that people who replaced saturated fat in their diets with polyunsaturated fat reduced their risk of coronary heart disease by 19 percent compared with control groups.
In 2013 the Sydney Diet Heart Study concluded that the benefits of the most abundant polyunsaturated fatty acid -- omega-6 linoleic acid -- have not been established. The authors did a meta-analysis of studies that considered polyunsaturated fats and showed that those where the omega-3 to omega-6 ratio was higher demonstrated beneficial results, while studies where the omega-6 content was higher did not show benefit.
One can see how this is a tough sell for the people who campaign for public health. It's hard to put "Replace Certain Fats with Certain Other Kinds of Fats That Have Even Longer and More Confusing Names If You Want to Live Longer – Maybe!" on a bumper sticker.
"The field of nutritional science can be murky," said Siri-Tarino.
So, How Should We Think of Fats?
Dariush Mozaffarian from the Harvard School of Public Health is one of the nation's leading experts on diet as it relates to disease. He said, "Total fat intake has little or no impact on health."
According to Mozaffarian, a person can have either a very high-fat or a very low-fat diet that is very healthy or a very high-fat or a very low-fat diet that is very unhealthy. How is that? A food can be either high-fat or low-fat and be healthy, or it can be high-fat or low-fat and be unhealthy. His point is: don't generalize when it comes to fats.
Mozaffarian advises avoiding unhealthy foods such as refined grains, sugars, starches, sugary drinks, processed meats and foods containing trans fats or high amounts of salt. He recommends replacing them with healthy vegetable fats, oils, fruits, vegetables, nuts, whole grains, fish, yogurt, vegetable oils -- especially extra-virgin olive oil -- and modest amounts of cheese.
"Total fat in any food, or in the diet, should be ignored," Mozaffarian said. "One should focus on eating more healthy foods."
Here's the Problem With ‘Low-Fat’ Foods
There's an unintended effect that occurs when people eat food that is labeled "low-fat." They eat more of it.
Cornell researchers found that putting "low-fat" labels on snack foods led to people eating up to 50 percent more than foods with labels that lacked a low-fat claim. People assume low-fat means fewer calories.
Researchers who went to a grocery store and looked at fat and calorie content of "low-fat" processed foods found that the foods contained 59 percent less fat but only 15 percent fewer calories. As the Cornell researchers point out, that's not enough to justify increased consumption.
Overweight individuals are especially susceptible to such labeling. Assured by the words "low-fat," those who took part in the study consumed 60 more calories than their thinner peers.
And here's a tip nutritionists know but has yet to makes its way into the mainstream. Fat satisfies appetite longer, which leads to eating less.
What’s Next for Fat?
In the years to come we're likely to learn that not only are certain fats harmful or good, but certain fatty acids in the context of different food sources are harmful or good. Now, polyunsaturated fats are recommended, but in the future, only certain polyunsaturated fats might be recommended.
The days of making broad, sweeping generalizations about food groups are coming to an end.
"The 1980s was all about 'low-fat,' so people increased their carbs," Siri-Tarino said. "Now health officials are saying to replace saturated fat with polyunsaturated or with monounsaturated."
She knows this is a hard sell.
"What does that mean to the person on the street?" she says. "Eat fish, nuts and avocado more often, and use fish to replace beef."
The Four Fats
All fats are not created equal. Some are unhealthy, and others convey big health benefits.
TRANS FATS: The consensus is these fats are unhealthy. They are found in meats, but are most common in processed foods such as cookies, breads and crackers. Trans fats increase the bad LDL cholesterol and reduce beneficial HDL cholesterol.
SATURATED FATS: These occur naturally and can be found in fatty beef, pork, poultry with skin, cream, butter, cheese and other dairy products made from whole or reduced-fat, such as 2 percent milk, among other foods. They contain dietary cholesterol.
POLYUNSATURATED FATS: Widely considered a "good fat" and a recommended part of a balanced diet, polyunsaturated fats are also known as omega-3 and omega-6 fatty acids. They're beneficial for cholesterol and for lowering triglycerides. Polyunsaturated fats can be found in fish, walnuts and cooking oils.
MONOUNSATURATED FATS: They're found in olive oil, avocados and most nuts. They contain nutrients and antioxidants. Eating monounsaturated fats improves blood cholesterol levels.