Does Eating Fat Make You Fat?

From the Lecture Series: The Skeptic’s Guide to Health, Medicine, and the Media

By Professor Roy Benaroch, M.D., Emory University

Does eating fat make you fat? Common sense would say, yes. This belief led to the rise of low-fat diets in the 1980s and 1990s. As you’ll learn, though, the answer is more complicated.

fatty foods and weight concept
(Image: Evan Lorne/Shutterstock)

How Obesity Is Stigmatized

Obesity, without a doubt, is the most significant public health hazard facing the United States and the rest of the developing world.

Two of three Americans are overweight, and one in three is obese. One in five children are also obese, and most of these children will continue to struggle with an unhealthy weight for the rest of their lives.

And yet, for a condition that’s so common, there’s an odd sort of dichotomy in the way our society looks at obesity. It’s as if there’s two kinds of obesity, or, at least, two ways of looking at obesity.

This is a transcript from the video series The Skeptic’s Guide to Health, Medicine, and the Media. Watch it now, on The Great Courses Plus.

These two angles insinuate themselves into headline and media coverage, and into the way doctors and health professionals care for their patients. If we’re going to make any progress defeating this public health nightmare, we’ve got to get the media and the doctors on the same side, working toward solutions that can really make a difference.

So far, it’s evident that we have not done a very good job.

Picture a typical news story about an issue related to obesity, maybe on CNN or in a magazine. What’s the image that comes to mind—the one they’re showing on the screen or on the page at the top of the story?

It’s nearly always the same: a torso, with the head cut off, of, well, a fat-looking person. One blogger referred to these photos as the “headless fatties.”

An oversize man eating a burger.
The stories use an image of an overweight individual, and that frames overweight as an individual’s problem. (Image: Ollyy/Shutterstock)

The stories use an image of an overweight individual, and that frames overweight as an individual’s problem. That is, a fat person is fat because of the decisions that person makes.

If they just didn’t eat so much, the thinking goes, they wouldn’t be fat. The Rudd Center for Food Policy and Obesity found that over 70 percent of news stories on the major television news outlets—CBS, ABC, Fox, and CNN—depicted overweight people in a negative or stigmatizing manner.

And yet, decades of trying to approach overweight as a problem caused by wrong decisions—by trying to get individuals to change their habits and eat less food—undeniably, hasn’t worked.

It turns out that maintaining a healthy wait is about more than an individual’s day-to-day meal choices. It’s also about hormones, physiologic regulation, and the way our genes and our changing environment have led to a perfect storm of the wrong kinds of foods being eaten by the wrong kinds of people.

This second side of obesity doesn’t seem to have captured the media’s attention; or when it does, the stories seem to get twisted around, leaving people confused, frustrated, and still overweight.

Learn more about the media and portraying weight loss

The Rise of Low-Fat Diets

To make progress against obesity, we have to decide what the roots are. What is the cause?

A logo showing low fat is good for health
(Image: DeiMosz/Shutterstock)

Find the cause, fix the problem—that sounds straightforward. For many years, the thinking about overweight was based on simple thermodynamics, or what’s been called the “energy balance” theory.

We consume food and that gives us the energy we need to stay warm and walk around or watch educational videos. That energy, by the way, is measured in calories.

They’re actually kilocalories, but we typically just say “calories” for short. A calorie is a measure of the energy content of a food.

The energy balance theory of weight control says that if you consume too many calories for your energy needs, the calories left over will be stored in your body, mostly as fat. Over time, eating more calories than you need will cause you to gain weight.

Conversely, eating fewer calories than needed will burn your stored energy, causing you to lose weight.

A natural conclusion one might make from this energy balance theory is that it’s a good idea to eat foods with fewer calories. Fill up on lower-calorie foods, the theory goes, and you’ll be more likely to stay at a healthy weight.

That was tried, for many years, as the guidance from dietary authorities, government recommendations, and physicians concentrated on low-fat eating.

Here’s a headline from The New York Times in June 1980: “Hidden Fat: The Hazards.” This is one of dozens of stories that year vilifying fat as a nutrient.

Prevention magazine ran articles like “Coexisting with Fat” in 1985, and “Five Ways to Cut the Fat” in 1987. The message here was that fat, any fat, was bad.

Many popular books and diets, too, that fervently hyped very low-fat diets. One of the best-known was developed by Dr. Dean Ornish—it became known as the Ornish diet—who suggested a very low-fat diet to help not only with weight, but to prevent or even reverse heart disease.

The press ate that up, so to speak, even though his breakthrough study in support of this idea involved only 37 patients. In Dr. Ornish’s defense, he had also stressed important lifestyle and exercise changes, and more recent editions of his popular diet books have moderated and refined his anti-fat stance.

Learn more about how to think like a skeptic when reading news in any medium

Why Did Low-Fat Diets Fail?

There are three main components of any food that make up its energy content, or the number of calories per serving: carbohydrates, proteins, and fats.

Carbs include simple sugars and starches, and they provide about 4 kcal per gram of food consumed. The energy content of protein is about the same, 4 kcal per gram. Fats, when broken down by the body, provide over twice the energy, 9 kcal per gram.

So if you’re trying to eat foods that give fewer calories per bite, it makes sense to decrease your consumption of high-caloric density fat. You can do this by eating foods naturally low in fat, like fruits and vegetables and whole grains.

And, guess what, that’s still a good idea. But what many people did, especially starting in the 1980s, was to shift their consumption of foods to those made with less fat, and, therefore, more people added carbohydrates.

By carbohydrates, we mean sugar, and especially a form of inexpensive sugar called high fructose corn syrup.

Well, that didn’t work, in part because our consumption of fat really didn’t decrease much. From 1970 to 2000, the average daily intake of calories from fat decreased by only 46. Not 46 percent, but by 46 net calories per day, which is close to negligible.

At the same time, the daily consumption of carbohydrate calories increased by 240. And of course, rates of obesity only continued to increase.

There’s even a name for this phenomenon: The Snackwell Effect, named after a popular line of cookies and treats introduced in 1992 by Nabisco.

People thought that the Snackwell cookies were healthier, because they were made with very little fat, even though they were packed with carbs and had about the same number of calories as ordinary cookies.

More calories means more weight gain, and that’s exactly what happened. Snackwells flew off the shelves, and people got fatter.

Learn more about shoddy science published in reputable medical journals

Changing Views on Fat

Was the advice to avoid fat wrong?

Maybe it wasn’t wrong, but it did become overblown and oversimplified?

Many fats are now considered so-called “good fats,” like olive and canola oils. These types of oils can help improve cardiovascular health.

Other types of fats, especially trans fat found in margarine and other processed foods, can increase your risk of health problems like stroke and cardiovascular disease.

Also, taking fat out of the diet did lead to a big surge in added carbohydrates. We’re seeing a backlash now, with headlines like, “Official Advice on Low-Fat Diet and Cholesterol Is Wrong, Says Health Charity” from The Guardian, or from the Huffington Post, “Why Low-Fat Diets Make You Fat (and Unhealthy).”

Again, these headlines are overblown. Fat, we know, was never the enemy. It’s your total caloric intake that matters, and a high-fat diet usually means a high-calorie diet.

good balanced diet concept - fats carbs and protein
(Image: Sashkin/Shutterstock)

The headlines have swung from fat is bad to carbs are bad, when in fact, either one is probably okay in moderation, and especially when consumed as part of a varied diet with few processed foods.

Here’s a headline that captured the changing viewpoint on fat very well, from the Chicago Tribune: “Dieticians: The War on Dietary Fat Missed the Point.”

Common Questions About Eating Fat

Q: Is eating fat good for you?

Although it’s important not to overdo the amount of fat in your diet, as that will increase your calorie intake and in turn lead to weight gain, it’s also important not to go overboard with a low-fat diet. Low-fat diets often end up increasing your sugar, carbohydrate, and total caloric intake. Additionally, fat provides you with energy (which helps to stave off hunger and prevent overeating) and aids the absorption of nutrients.

Q: What happens when you eat fat?

The digestion process is slower with fats than with carbohydrates. Once you digest fats, some of the fat is immediately converted to energy while the remainder is saved to give you energy when you need it later; for instance, when you workout or go a long time between meals, this stored energy keeps you going.

Q: Should I eat fat to lose weight?

Although it seems paradoxical, eating fat can actually help you lose weight. When you eat carbohydrates, your blood sugar levels go up and you become hungry again quickly. By contrast, eating fat helps you to stave off hunger and thus reduce your total caloric intake.

Q: What happens if you don’t eat enough fat?

Not eating enough fat will result in less energy, hunger pangs, dry skin, and increased sensitivity to cold.

This article was updated on 7/26/2019

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