Oil free diets are regularly discussed within the plant-based and vegan community. While some plant-based doctors promote oil free diets, the research on this type of diet is limited.
Following a plant-based diet can be challenging enough, so is adding this additional layer of restriction needed? This article covers what you need to know about the pros and cons of oil free eating.
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What is an Oil Free Diet?
Oil free diets are just as they sound: a diet that doesn’t include oil in any form. Someone following an oil free diet would not use liquid oil, margarine/ butter products, or any foods that contain these ingredients.
While anyone could follow an oil free diet, I’ve personally only seen it popularized as a way of eating among the plant-based/vegan community - specifically those who follow a “whole food plant-based” diet approach.
Essentially, these people consume only whole, unprocessed plant-based foods. Since oil is processed, it’s off the list of foods they’ll consume.
Why Do People Follow Oil Free Diets?
The concept of oil free diets originated among some doctors who promote whole food, plant-based diets. There are many reasons why these doctors (and others who adopted this way of thinking) promote this style of eating.
The most cited reasons include:
- Oil is processed
- Oil is high in calories and void of nutrition
- Low fat/ no oil diets are better for weight
- Oil harms the endothelium
- Oil free diets are better for heart health
The message being spread by supporters of oil free eating is often very clear and powerful: avoid oil at all costs as it’s void of nutrition and harmful to health.
While these messages are stated repeatedly by oil free diet promoters, it does not mean they’re true. It’s important to look at both sides of the story on how oil can impact health.
Let’s go into detail on the research for and against consuming oils.
Research on Oil Free Diets
There are a few studies that look specifically at oil free diets or the direct impact of consuming oils. Other studies referenced in support of oil free eating look at low-fat diets in general, because research on strict oil free eating is limited.
Before we get into research on oils, here’s a brief overview of the role fat consumption plays in human health.
This topic needs a full review separate from this discussion of oil, but the main findings related to fat intake seem to be:
- The type of fat eaten is a more important consideration, rather than the amount 1, 2, 3, 4, 5, 6
- Trans fats are almost always associated with negative health outcomes 7, 8
- Saturated fats are often associated with negative health outcomes 1, 2, 3, 4, 7
- Unsaturated fats are often associated with positive health outcomes 1, 2, 5, 9, 10
Finding a diet pattern that an individual enjoys and can maintain long term is also important (and often overlooked).
To truly understand the impact of oil free diets, here’s research specific to oil free eating and the different arguments for a no oil diet.
Oil is Processed and Only Whole Foods Should be Eaten
A common first point made by those who promote oil free diets is that oils are highly processed and should be avoided. However, the fact that oils are processed is not reason enough to avoid them, in my opinion.
First, not all oils are highly processed, some are minimally processed (extra virgin oils, for example) 13.
Secondly, most foods people eat are processed in some way and that doesn’t mean they are unhealthy or “bad”. Peeling, cutting, boiling, steaming, baking, freezing, fermenting, dehydrating, canning and pickling are examples of processes that foods go through.
Often, when people refer to processed foods as being “bad” they think of refined foods. Oils are a refined food which means some of the nutrients, like fiber, have been removed.
It’s often cited that rather than using oil, the whole food ingredient oil is made from should be eaten instead (olives instead of olive oil). This way, you won’t miss the fiber and other nutrients whole food offers.
I disagree with this line of thinking because those “lost” nutrients are often found in other foods within the same meal.
With nutrition, the whole meal or dietary pattern need to be considered, not just one ingredient. While oils don’t contain fiber, they aren’t consumed on their own; they’re added to a meal.
If that meal contains vegetables, whole grains, legumes and other high-antioxidant, nutrient-rich foods, you’re likely meeting fiber intake recommendations and meeting nutrient needs for other vitamins and minerals that may have been lost while processing the oil. Adding oil to a meal doesn’t remove the benefits of the other ingredients in that meal.
You can consume whole foods and oils. It doesn’t have to be one or the other. All foods can fit into an overall balanced diet.
Summary: There are different levels of processing used in making oils. Processing, in and of itself, doesn’t mean a food should be avoided. The nutrients lost when processing oil can be found in many other foods; these foods can be included in a meal that contains oil.
Oil is High in Calories and Void of Nutrition
One of the main reasons why someone would avoid oil is that oil is very high in calories. There are, on average, 120 calories per tablespoon of oil.
This is a high number of calories for a small volume of food, but calories aren’t “bad”. Calories are simply a measurement of the amount of energy in a food.
Adding fats to a meal can improve taste and enjoyment of a meal, leading to better satisfaction and satiation, among other benefits.
Despite not containing fiber, oils do contain nutrients like essential fatty acids, fat-soluble vitamins and antioxidants (in varying amounts depending on the type of oil).
You can eat a high fiber meal that also contains oil, which may keep you feeling full for longer. Protein in a meal can also help keep you feeling fuller for longer.
One tablespoon of olive oil has: 14, 15
- 2 mg vitamin E (13 % of recommended daily intake)
- 8 ug vitamin K (6% of recommended daily intake for males; 8% for females)
- 0.1 g omega 3 (6% of recommended daily intake for males; 9% for females)
- 1.3 g omega 6 (7% of recommended daily intake for males; 10% for females)
While these aren’t huge numbers, they aren’t insignificant either. Other types of oil like flaxseed and walnut are very high in essential omega-3 fats.
There are also antioxidants present in olive oil and other virgin (or cold-pressed) oils. While the amount of antioxidants depends on the type of oil, these antioxidants can benefit health 16, 17, 18, 19, 20, 21, 22.
Summary: While oils are high in calories, they contain essential nutrients (in varying levels depending on the oil).
Low Fat/ No Oil Diets are Better for Weight
Those promoting oil free diets also generally recommend low fat, or very-low fat, diets. This argument is often tied to weight management with belief that low fat/ oil free diets are superior for weight loss.
Research into weight loss is inconclusive because the type of diet is often not important.
Low-fat, high-fat, low-carb, high-protein, Mediterranean, intermittent fasting, vegetarian/ plant-based dieting have all been shown, in one study or another, to result in weight loss 23, 24.
Some of these diet types may also offer additional health outcomes beyond weight loss.
An individual’s preferences and adherence to the diet, in particular the ability to maintain the diet long-term, are critical factors in determining which eating pattern is best for each individual 23, 24.
Focusing on which diet is “best”, from a weight loss perspective, misses the point, in my opinion. One can use valid research to support any number of weight loss approaches 23, 24. Furthermore, health benefits can be achieved with lifestyle changes, even without weight loss 25, 26.
Beyond the fact that almost any diet can “work”, research suggests that a focus on weight loss is not helpful and may be harmful 25, 26.
Weight loss is not sustainable for most people and a focus on weight loss perpetuates weight stigma, which can result in worse health outcomes 27, 28.
Focusing on other health outcomes may be of greater benefit (rather than focusing on weight loss or ways to achieve weight loss).
Promoting restrictive eating patterns (like an oil free diet) for weight loss is not necessary to lose or maintain weight. Finding a sustainable lifestyle that focuses on health outcomes, separate from weight, may be a better approach.
This assumes that someone wants to make dietary/ lifestyle changes for their health.
Summary: There are many diets that can help with weight management, including those that are higher in fat and/ or contain oil. Focusing on weight loss as a health outcome may do more harm than good (other measures of health may be a better focus). How well a person can maintain a dietary change, in the long-term, is essential.
Some research suggests consumption of oil harms the endothelium (inner lining of the arteries) and this could be a risk factor for heart disease and other diseases 29.
One frequently referenced study looked at the effect of high fat meals with 50 grams of fat from either olive oil, canola oil or salmon along with crackers or bread 30. Only the olive oil meal showed a significant, negative effect on the endothelium 30. This negative effect was reduced to the point where it was no longer significant by adding antioxidants to the meal (either vitamin C + vitamin E or a salad with balsamic vinegar) 30.
A second study that’s also frequently referenced in support of oil free diets looked at olive, soybean and palm oils 31. In this study, participants ate a potato soup meal with 60 mL of oil which is about 57 grams of fat (the soup was simply potatoes, water, salt and oil) 31.
All three oils showed similar harmful effects on the endothelium 31. These results have not been repeated in other studies.
One other study looked at consuming olive oils that are high and low in antioxidants, paired with wine that was either high or low in antioxidants 20. This study used a vegetable soup with 50 grams of olive oil, 2 slices of white bread and 250 mL of wine for the test meals 20.
They found high antioxidant olive oil and high antioxidant wine, together, improved endothelial function after a meal 20.
Far from showing any harm, there was a significant improvement in endothelial function after a high fat meal that was rich in antioxidants 20.
Furthermore, there weren’t any significant detrimental effects found for the consumption of low antioxidant olive oil and/or low antioxidant wine pairings 20.
An additional study found a diet rich in monounsaturated fats benefited endothelial function compared to a high saturated fat diet and compared to a lower fat diet enriched with omega-3s (ALA) 2.
It’s important to note the very large amounts of fat used in these studies, typically about 50 grams of fat in one meal. This is significantly more than an average, home-cooked meal contains (unless deep frying foods). It would be very helpful to research smaller amounts of fat/ oils to observe if similar effects are found (but, to my knowledge, this research doesn't exist).
Additional research has also found beneficial effects of oil on endothelial function 19, 32, 33.
There are many complex factors that could help explain these differing results. In my opinion, mixed research results are not a convincing reason to avoid oil, but they show benefits of including antioxidant-rich foods with oil-containing meals.
Summary: The research on oil intake and endothelial function is mixed, with studies showing negative, positive or no effects. These studies use very high amounts of fat in the test meals, more than what an average home cooked meal would contain.
There are a few other studies that point to heart health benefits of using no oil. One that’s commonly cited showed people with heart disease (have already had a heart attack) put onto a completely whole food, plant-based diet, including the elimination of oil 34.
Further cardiac events were found to be extremely low in the people who followed this dietary protocol 34.
As with any study, there are limitations to this research. The most important ones to consider with this study is it was not a randomized trial and there was no control group. The study notes that participants were self-selected and “very determined” which could be why the adherence rate was high 34.
Another study looked at an “intensive lifestyle program” (10% fat vegetarian diet, moderate exercise, stress management training, smoking cessation and group psychosocial support) compared to “usual treatment” (following advice of their physicians) for patients with established coronary atherosclerosis (heart disease) 35.
This study found those in the lifestyle intervention group had better outcomes across different markers of heart health 35. Keep in mind they were comparing a drastic lifestyle change against minimal change (we know that “usual treatment” is ineffective for heart disease).
These are very interesting studies, and while I don’t think they should be ignored, it’s important to take in a balance of evidence.
Other research suggests that dietary patterns including oils and/or moderate amounts of fats are beneficial for heart health 2, 4, 5, 6, 10, 11, 12, 19, 20, 36.
Those who promote oil free plant-based diets often compare it to a Mediterranean diet, with the conclusion that an oil free plant-based diet is superior for heart health. However, these two diets are very different and, to my knowledge, have not been studied side-by-side (therefore making direct comparisons is not possible).
The Mediterranean diet is often viewed as a plant-based diet, but can include dairy, eggs, meat (including small amounts of red meat) and promotes eating fish.
To date, I haven’t seen research comparing a fully plant-based diet containing oils to one without oils.
Without this research, it’s hard to know if the benefits shown in oil-free diet research is due to the lack of oils, the lack of other animal products alone, or another factor entirely.
With an abundance of research demonstrating benefits of consuming olive oil (in particular) and eating patterns that contain oil, I cannot conclude that eliminating oils is necessary, especially for those already following a plant-based diet.
Summary: Research supports that unsaturated fats, including oils, are beneficial for heart health. Research on oil free diets and heart health are limited and more research is needed (particularly on plant-based diets that include varying levels of oil intake).
Benefits of Consuming Oil
It’s important to look at both sides of any nutrition topic. In this case, that means examining research on the health benefits of consuming oil.
The type of fat consumed is a critical factor for this discussion. Unsaturated fats (polyunsaturated and monounsaturated) seem to be beneficial for general health and heart health in particular 1, 4, 10, 11, 12.
There are many research studies about dietary patterns that contain oil, even oil in fairly large amounts, which benefit health conditions including heart health.
Other proposed benefits of using oils include:
These benefits are for consuming adequate amounts of fat, whether from oils or other sources 42. I’ve included them because the focus of oil free diets is often to consume a low fat diet, which would minimize or eliminate these benefits.
While some people may do well with very low-fat eating, many people benefit from moderate fat intake (especially people with menstrual cycles) 42.
The benefits above are in addition to research that support the benefits of unsaturated fats, including those from oils, for heart health.
There are other reasons I believe including oils in a plant-based or vegan diet is beneficial. While there isn’t research specifically examining these issues, I think it’s important to consider that including oils in a diet may help with:
- Enjoying cultural foods
- Having a varied diet
- Enjoying foods without guilt or stress
- Maintaining a vegan lifestyle long-term
Nutrition Concerns of Oil Free Diets
Oil free diets are often promoted as the best way to consume a fully whole food, plant-based diet. Since eating whole, plant-based food is generally considered healthy, some may wonder if there’s any concerns with following an oil free diet.
To my knowledge, there are no studies specifically examining possible negative effects of no oil diets.
Below are concerns that myself or others have raised about oil free diets.
Meeting Fat Intake Requirements
With an oil free diet, one must still meet intake requirements for essential fatty acids, fat-soluble vitamins and essential nutrients (vitamins A, D, E, K and omega-3s and omega-6s).
Fats and oil can help nutrient absorption from a meal, therefore it’s important to include at least some fat in every meal 37, 38, 39.
If one were to only consume whole food sources of fats from plant-based options, they would be limited to getting fats from avocados, nuts, seeds, soybeans and olives (plus coconut, although oil-free dieters often avoid this due to high amounts of saturated fats).
It’s possible to meet fat intake requirements from whole food sources of fat alone, but this may not be practical.
Cost, culture, preferences, lifestyle and other factors need to be taken into account when providing dietary recommendations; a strict elimination of oil doesn’t take these factors into account. It is not a practical lifestyle for many people.
Restrictive Dieting and Disordered Eating
Oil free diets are almost always promoted within the plant-based/vegan community.
Given a plant-based or vegan diet is already quite restrictive, adding another layer of restriction can be challenging and stressful. It may also lead to disordered eating.
Food restriction is a symptom of many eating disorders. Restriction of types and amounts of food, and following food rules, are some factors that may lead to disordered eating 43, 44.
While promoting “healthy eating” we must not overlook the harms and common signs of eating disorders.
Surprisingly, I rarely see cost as a reason why someone may not want, or be able, to follow an oil free diet.
The primary sources of fats on a no oil diet are nuts, seeds and avocados. These foods are expensive and may not be accessible to different groups of people.
Healthcare professionals need to recognize there are a diverse range of people in this world and not everyone is able to afford the types of foods research shows is “best”.
What is truly best is feeding yourself and family without shame for what, or how, you eat.
Also, people often say that eating well is an investment in your health and will save you money on future healthcare bills. This only works if you have the money now to “invest” in your health.
Taste and Enjoyment of Food
Fats and oils make food taste better. Research shows that adding fats (oil) to a meal makes it more palatable and satisfying 40.
Furthermore, many flavor compounds found in herbs and spices are fat soluble. This means they require fats to bond with to get the full flavor when you eat it 45.
There’s a reason many recipes start with sautéing onions or spices in oil before adding other ingredients - it enhances the taste of the dish. I believe that enjoying the full flavors of every meal is an important way to maintain a nutritious, balanced diet and enjoy eating.
Food is so much more than just nutrition. It’s memories, culture, connection with others and provides pleasure. In my opinion, enjoying food is an important aspect of life and health.
Restrictive diets can strip us of our enjoyment of food and lead to feelings of stress, guilt or shame.
If a restrictive diet leads you to enjoy food less and causes feelings of stress, guilt or shame, are you really doing yourself any good?
If you have concerns about your eating patterns or feelings related to eating different foods, please speak with your primary care provider.
Who Could Benefit from a Reduced Oil Diet?
I believe there’s simply not enough research to promote oil free diets in a generalized way (to everyone in the world).
Additionally, I’d caution against following any diet that has a strict focus on elimination of foods/ food groups for the sake of “health” (veganism is a different discussion as the focus of veganism is ethics). This is because of the potential harm that restrictive diets may pose, especially in terms of disordered eating.
Many “healthy” eating behaviors are actually disordered eating in disguise. If you have any concerns about your eating habits, please talk with your primary care provider.
When looking at the landscape of dietary advice, you could create quite the list of foods to avoid, depending on who you listen to.
People like to live in extremes, especially when it comes to diet. Often, people think if they don’t make a huge change, no benefits will come. This is one reason some people promote a no oil diet whereas others promote ketogenic diets (a diet very high in fat).
Also, people typically want to feel part of a group and find comfort in following a dietary philosophy where they can find other like-minded people for support and encouragement.
Moderation, which is practical, reasonable and sustainable (and often a great approach to mental and physical health) is often laughed at in these diet extremes.
If you want to avoid oil, ensure that you:
- Meet intake requirements of essential fats
- Meet intake requirements of fat-soluble vitamins
- Eat in a way that doesn’t result in disordered eating thoughts and/or behaviors
- Enjoy your meals and eat a variety of foods
- Eat with others in a joyous way, including at holidays or other gatherings
- Don’t develop feelings of stress related to what foods you can or cannot eat
- Don’t feel guilt or shame when eating something that contains oil
- Don’t become fixated on “healthy eating”
If you have any concerns with the list above, please speak with your primary care provider.
Consume oils or avoid oils; either way it's your diet and your choice!
Summary: Oil Free Diets
Oil free diets are often promoted with a focus on eating only whole plant-based foods. Because research on oil free diets is limited, benefits associated with this diet type are often sourced from low fat or very low fat diet research.
With nutrition research, it’s important to look at both sides of the story. The other side of the oil free story is a body of research that supports inclusion of unsaturated fats, from a variety of foods, including oils.
Restrictive diets can make eating unnecessarily complicated and stressful, and there is potential for development of disordered eating behaviors when one becomes too focused on everything they consume. Adding mental stress is not the way to a healthful life; I believe mental health is equally as important as other aspects of health!
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- Dietary fat types and 4-year cognitive change in community-dwelling older women
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- Unsaturated fatty acids improve atherosclerosis markers in obese and overweight non-diabetic elderly patients
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- How olive oil is processed
- Dietary reference intakes tables
- Canadian nutrient file
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- Optimal diet strategies for weight loss and weight loss maintenance
- Scientific evidence of diets for weight loss: Different macronutrient composition, intermittent fasting and popular diets
- Challenging assumptions in obesity research
- The weight-inclusive versus weight-normative approach to health: Evaluating the evidence for prioritizing well-being over weight loss
- Maintenance of lost weight and long-term management of obesity
- How and why weight stigma drives the obesity ‘epidemic’ and harms health
- The vascular endothelium and human diseases
- The postprandial effect of components of the Mediterranean diet on endothelial function
- Olive, soybean and palm oils intake have a similar acute detrimental effect over the endothelial function in healthy young subject
- Acute effects of monounsaturated fatty acids with and without omega-3 fatty acids on vascular reactivity in individuals with type 2 diabetes
- A Mediterranean diet supplemented with extra virgin olive oil or nuts improved endothelial markers involved in blood pressure control in hypertensive women
- A way to reverse CAD?
- Intensive lifestyle changes for reversal of coronary heart disease
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- Avocado consumption enhances human postprandial provitamin A absorption and conversion from a novel high-beta-carotene tomato sauce from carrots
- Carotenoid absorption from salad and salsa by humans is enhanced by the addition of avocado or avocado oil
- Effect of high- versus low-fat meal on serum 25-hydroxyvitamin D levels after a single oral dose of vitamin D: A single-blind, parallel, randomized trial
- Is fat taste ready for primetime?
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- The role of lipids in aroma/food matrix interactions in complex liquid model systems
This reference list is not intended to be comprehensive.
About Nicole Stevens
Nicole is a vegan Registered Dietitian (RD) and founder of Lettuce Veg Out.
She helps people thrive on a vegan diet with balanced recipes and easy-to-understand nutrition science.
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