Should You Eliminate Oil From Your Diet?

Some popular diet trends recommend eliminating all forms of oil from your diet—including oils that are often promoted as healthful, such as olive oil. Is an oil-free diet healthier?

Nutrition Diva listener Joy recently asked about this in a Facebook discussion. “What do you think about the idea that oil is unhealthy and should be avoided?,” she wrote. “I've noticed that some plant-based recipe blogs I like highlight their oil-free recipes. And a doctor told me I should work on eliminating ALL oil (not fats, just oil) from my diet. If you haven't done a podcast on this topic, please think about covering it!”

Your wish is my command, Joy. Let’s take a closer look at some of the arguments against oil.

Is Oil Unhealthy Because it is Processed?

The Argument: 

Oils are generally extracted from whole foods. Olive oil is pressed from whole olives, corn oil is pressed from corn, and so on. In the process of extracting the fat, valuable nutrients (such as fiber) are left behind. Oil is also much more calorie dense than the whole foods it is pressed from.

This is similar to arguments I’ve made against fruit juice. When we squeeze an orange, we remove the fiber and end up with a more concentrated source of sugar and calories. We can also drink a glass of juice much more quickly than we can eat an orange, and this can lead to overconsumption.

The Counterargument:

One difference here is that no-one is going to drink a glass of olive oil instead of eating a few olives.

Olive oil is most commonly used to dress a salad or roast vegetables. Does adding oil to your salad add calories? You bet. Does it make those vegetables less nutritious? Not at all. In fact, adding oil to your salad helps you absorb more of the nutrients in those vegetables. And if it makes those vegetables more appealing and palatable, so that you eat more of them (and less of other things), it’s a win all the way around.

See also: What's the Most Nutritious Way to Eat Vegetables?

This seems to be the case for Cheryl, who posted, “Since I stopped limiting my olive oil years ago, I've eaten way more vegetables—because they taste great with oil and not as great without it.”

As for valuable nutrients being left behind, many of the most beneficial nutrients in olives, nuts, seeds, and avocados—such as omega-3 fatty acids, phytosterols, vitamin E, and polyphenols—are fat soluble. These nutrients are not only present in the oil, but they are often in more concentrated amounts than you’d get from eating the whole foods.

Can Consuming Oil Lead to Weight Gain?

The Argument:

One website promoting oil-free diets claims that “Oil...has more calories per gram than any other food...and without any fiber or water in it, oil lacks the bulk to convey to your senses how many calories you have eaten; this virtually guarantees you will consume more calories at the meal than you need.”

The Counterargument:

It’s absolutely true that oil is a concentrated source of calories but I don’t buy the argument that including oil in your diet will inevitably lead you to consume too many calories and gain weight.

As I explained in my episodes on satiety and satiation, water and fiber add volume to foods, which helps fill the stomach. That’s one of the reasons that I encourage you to eat vegetables whenever you can. But fat can help you eat less through other mechanisms—by stimulating the release of gastrointestinal hormones that reduce the desire to eat, and slowing down the absorption of carbohydrates from your meal, which leads to steadier blood sugar levels.  

Combining vegetables (with their high water and fiber content) with healthy fats such as those found in olive oil can be a winning combination in terms of nutrition, taste, and appetite control.  

See also: Why am I So Hungry After Eating Vegetables?

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The Mediterranean diet provides another counterargument to the claim that including oil in your diet will lead you to gain weight. This dietary pattern gets a large portion of its calories from fat, in general, and olive oil, in particular. And yet those who follow a Mediterranean diet pattern are less likely to be overweight than those who follow a standard American diet, which is somewhat lower in fat. (It’s also lower in vegetables.)

Whether or not oil is healthful or unhealthful depends a lot on the company it keeps. Eating a lot of potato chips, french fries, cakes, cookies, and other pastries could definitely lead to excessive calorie consumption. But the oil is not what makes these foods problematic. They also contain high amounts of salt, sugar, and/or refined white flour.

Olive and avocado oil are both high in heart healthy monounsaturated fats and polyphenols.

If you are minimizing your intake of fried foods, refined grains and added sugars, I’m not that worried about how much olive oil you’re consuming.

Some Oils are Healthier Than Others

Although I don't think there's a good argument for eliminating all oil from your diet, some oils are definitely healthier than others.

• Olive and avocado oil are both high in heart healthy monounsaturated fats and polyphenols.
• Coconut oil is very stable at high temperatures, so it’s a good choice for high heat cooking.
• Canola and walnut oil are both good sources of omega-3 fats.

One of the sillier arguments I saw against oils is that "they may also lead to increased bleeding through thinning of the blood;" This blood-thinning action, which helps to lower the risk of blood clots and stroke, is  one of the reasons that omega-3 fats lower the risk of heart disease. 

Vegetable oils pressed from corn, soy, and sunflower seeds are perhaps the least healthful choices. These oils are very high in polyunsaturated fats, which can create harmful compounds when heated. They are also quite high in omega-6 fats, which can prevent those healthy omega-3s from doing their job.  

Which Oils Should You Use or Avoid?

Because different oils offer different advantages, I use a variety of different oils. Olive oil is my primary cooking oil. I use coconut oil if I’m stir-frying at high temperatures. I might also choose coconut, walnut, toasted sesame, or another specialty oil for the specific flavor it contributes. On the other end of the spectrum, I keep a bottle of canola oil around for those times when I need a very neutral flavor. I generally do not use corn, soy, or other vegetable oils.

What do you use in your kitchen? Or do you avoid oil? Post your thoughts below or on the Nutrition Diva facebook page. 

Image of different kinds of cooking oils © Shutterstock