The WFPB Diet Debate
By Dina Aronson, MS, RDN
Vol. 24 No. 7 P. 22
Today’s Dietitian explores the research on the low-fat vs higher-fat versions of the whole-foods plant-based diet and their impact on overall health.
The popularity of plant-based diets has skyrocketed over the past decade. About 3% and 5% of Americans say they’re vegan and vegetarian, respectively. 1 According to one survey of more than 1,000 Americans, 12% of respondents reported following a plant-based diet in the past year.2 And with this upsurge, several variants of the plant-based theme have emerged. One, in particular, is the whole-foods plant-based (WFPB) diet, which is gaining traction and is the subject of controversy.
What is a WFPB diet? Like most plant-based diet variants, there are different definitions and interpretations. These variants lie on a continuum of purity, from a mixed diet containing some whole plant foods to a diet based entirely on minimally processed plant foods in their whole form, with no foods of animal origin and no hyperprocessed ingredients such as refined flour, sugar, and oils. But most would agree it’s a vegan eating pattern, which excludes all animal products, emphasizes plant foods as close to their natural state as possible, and minimizes or omits heavily processed plant foods. The distinction between “vegan” and “whole foods plant-based” is important because a vegan diet isn’t necessarily a high-quality diet. Meals centered around refined grains, sugary beverages, added sugars, excessive fats, and hyperprocessed vegan meat and dairy substitutes can still be vegan but not healthful. A WFPB diet is high in quality. It’s designed to optimize health, as it’s consistent with an extensive body of research showing that healthful, properly planned plant-based diets are associated with reduced risk of mortality, CVD, type 2 diabetes, certain cancers, hypertension, hypercholesterolemia, and obesity.3
Among proponents of the WFPB diet, there are two camps: the low-fat approach and the more liberalized dietary fat approach. The low-fat version encourages fruits, vegetables, whole grains, and beans, but restricts portions of higher-fat foods (eg, nuts, seeds, avocados, and olives) and omits added oils; the fat content is about 10%.4,5 The other approach is more liberal with respect to added fats, allowing a higher percentage of fat from whole food sources and some from high-quality cooking oils such as olive and canola oils.
At the heart of the controversy is research supporting both dietary patterns, which are treated as mutually exclusive, but, when we explore the nuances, often they’re not.
The peer-reviewed studies can be used to advocate for either diet.4-6 However, what’s missing is reliable scientific evidence comparing the two approaches. When comparing a therapeutic diet to a less healthful baseline, results can be powerful. Comparing similar plant-based eating patterns can be challenging; it takes years to develop chronic disease, so clinical trials often are of limited value. Observational studies looking at large populations over time don’t have enough data on these specific eating patterns. Given the standard Western dietary patterns are baseline, these two plant-based diets are more alike than different—but still, there’s controversy. Dietitians may ask: “As an eater approaches a pure, no-oil, low-fat WFPB diet, is there a point at which the law of diminishing returns kicks in?” “Is stricter necessarily more healthful? What if both work to optimize health?” For example, while it’s clear that a WFPB low-fat diet does reduce risk of further cardiac events in people with heart disease, no study compares that intervention to a similar but more liberalized WFPB diet.4-6
Exploring the Controversy
Considering this limitation in the scientific literature, what follows is a discussion of the most often cited arguments for these dietary approaches along with supporting research.
Heart Disease Reversal
A low-fat plant-based diet has been shown to not only mitigate but reverse heart disease progression among subjects with extensive cardiac damage, having suffered from one or more cardiac events (eg, heart attack or stroke). In fact, those who adhered to a no-oil, WFPB diet lowered their risk of further cardiac events.5,6
However, these interventions had no control groups or comparison groups. When eliminating dairy, eggs, poultry, fish, meat, and oil, the mechanisms for disease reversal are potentially hundreds. Researchers don’t know whether the benefits are from the foods eliminated, the foods replaced, the overall substitutions, or the weight loss that ensued—or a combination. There’s no data to suggest that an extra handful of nuts or a teaspoon of olive oil would compromise the benefits.
So, while a person with advanced CVD may benefit from the most restrictive of WFPB therapeutic diets, this doesn’t mean healthy people will fare better over time with that level of restriction.
Part of the debate regarding WFPB diets is consumption of oil, which has a high-calorie density. A hallmark distinction of WFPB diets is their nutrient density or concentration of protective nutrients among a given calorie allotment. Adding oil (120 kcal/T) potentially could displace other, more nutrient-dense food sources. According to Julieanna Hever, MS, RD, CPT, author of The Choose You Now Diet and Plant-Based Nutrition (Idiot’s Guide), “Oil is a processed food. It’s the pure fat that has been extracted from a whole plant, removing all of the fiber and most of the nutrition. Nutritionally, it’s unnecessary when food isn’t scarce and calories can be found in abundance.” In addition, elimination of oil may simplify weight loss, if that’s the goal.
Added oils aren’t essential, but they do play a role in many traditional cuisines, cooking techniques, and palatability (eg, mouthfeel, flavor, enjoyment). They also provide nutrients, namely essential and nonessential fatty acids and vitamins E and K. Many studies have focused on olive oil in particular, as it’s a mainstay in many traditional diets, particularly in Mediterranean diet patterns, contributing around 40% of fat calories. The majority of studies have found beneficial effects of olive oil consumption, especially when the olive oil displaces saturated fats.7
Neither an RDA nor Adequate Intake has been set for fat consumption because there’s insufficient evidence to define intake levels at which risk of inadequacy or chronic disease prevention occurs.8 An acceptable range has been set at 20% to 35% of calories, as this is the level at which intakes generally fall when following recommendations to lower chronic disease risk.8 However, fat percentage alone is of limited value since it doesn’t account for overall diet quality, which is a better predictor of health than macronutrient distribution. If the diet is nutritionally adequate and mainly composed of whole plant foods, macronutrient distributions can vary significantly and still support optimal health.
For example, people living in the Blue Zones have the lowest rates of chronic disease and greatest longevity. The Okinawan region of Japan, one of the Blue Zones, focuses on a diet that’s predominantly WFPB and very low in fat (10% of calories). Nearly 6,000 miles away, on the island of Ikaria, Greece, the Blue Zone population enjoys a predominantly WFPB diet that’s much higher in fat (40% of calories), as it emphasizes olive oil. Both populations live long, healthful lives relatively free of age-related disease.9
Despite the favorable health outcomes of those consuming a high percentage of plant fats, dietary fat has been purported to negatively impact endothelial function, which plays a role in the development of cardiovascular risk factors. Several studies have reported that high-fat meals adversely affect endothelial function, particularly in high doses and when consuming foods high in saturated fat (eg, dairy, processed meats).10
Two small studies often are cited as evidence for the recommendation to avoid all oil. One is a study from 2000 looking at endothelial function in 10 men after consuming meals containing 50 g of fat from different sources.11 The other is a study from 2007 looking at endothelial function also in 10 men after consuming a large quantity of different types of oil at one meal (60 mL, or about 55 g of fat).12 Both concluded that ingestion compromised endothelial cellular function for all types of oil, including olive oil. While these findings are cause for further investigation, they’re not the final word. Not only have these findings not been replicated in large studies, but the preponderance of research reports the opposite effect and discusses how different factors such as dose-response, individual metabolic status, fat source, accompanying meal components, and more have a significant effect on the outcomes.13-17 Other studies suggest synergistic effects of certain fats with other meal components such as antioxidants.18,19 After all, people eat mixed meals, not isolated fats. A study from 2021 compared different types of olive oil on endothelial function and found that extra-virgin olive oil significantly improved endothelial function in adults at risk of type 2 diabetes, while a refined olive oil did not.20 According to David Katz, MD, MPH, a lifestyle medicine physician, researcher, and one of the study’s authors, “The quality of the olive oil makes all the difference. In our studies using good quality extra-virgin olive oil, consumption improved endothelial function.” He also says that while olive oil largely has been shown to be protective, diets can be great with or without olive oil, or low or high in fat. “No one food accounts for the net effects of the overall diet,” Katz explains.
Even though the traditional Mediterranean diet isn’t exclusively plant based (ie, it contains some seafood and dairy but otherwise little meat), it’s notable here because it’s plant predominant with high levels of fiber and protective nutrients, and it’s based on fresh, whole foods. It has years of scientific evidence behind it to support its strong association with health benefits. In a systematic review, the Mediterranean diet showed favorable effects on lipoprotein levels, endothelium vasodilatation, insulin resistance, metabolic syndrome, antioxidant capacity, myocardial and cardiovascular mortality, and cancer incidence in obese patients and in those with previous myocardial infarction.21 Studies examining the active ingredients of a Mediterranean diet have placed a particular emphasis on high intake of vegetables, fruits, nuts, olive oil, and legumes; moderate intake of alcohol; and limited consumption of meat.22 The dietary pattern contains about 35% to 40% fat, mainly from olive oil. These characteristics can be applied to a WFPB diet to create a pattern that, for some, may be more palatable and satiating, and easier to follow than those limiting dietary fat. In a recent randomized crossover trial of 62 overweight adults, researchers compared the Mediterranean diet with a low-fat vegan diet to determine which better improved weight and cardiometabolic risk factors. Researchers found the vegan diet led to greater weight loss, better lipid profiles, and insulin sensitivity, but the Mediterranean diet produced lower blood pressure.23
Essential Fatty Acid Adequacy
Plant-based diets are relatively low in alpha-linolenic acid compared with linoleic acid and provide little, if any, EPA and DHA.24 Clinical studies suggest that tissue levels of long-chain omega-3 fatty acids are depressed in vegetarians, particularly in vegans.24The Dietary Reference Intakes’ Adequate Intake recommendations for omega-3 fats for most adults are 1.1 g for females (higher for pregnancy and lactation) and 1.6 g for males.8 These levels can be difficult to achieve when dietary fats are extremely restricted.
Below are three examples of 2,000-kcal WFPB menus (portions adjusted for isocaloric comparisons) with varied significant fat sources: none, whole foods only, and whole foods plus oil.
#1 NO OIL, NUTS, OR SEEDS (LOW-FAT)
Breakfast: 1 cup steel cut oatmeal, six dates, 1 cup mixed berries
Snack: One medium banana, 3 cups plain popcorn
Lunch: Lentil salad made from 1 cup lentils, 1/2 cup diced vegetables, and 1/2 lemon blended with water; 1 cup cooked kale; 1 cup brown rice; and one medium apple
Snack: 1/3 cup fat-free hummus with 2 cups raw vegetables
Dinner: Power bowl made with 2 cups spinach, 11/2 cups quinoa, 1/3 cup kidney beans, 1/4 cup corn, six slices of onion, six cherry tomatoes, three carrot strips, and one baked sweet potato
Percent of calories from fat: 7.8%; omega-3 fats: 0.8 g
#2 NO OIL, WITH NUTS, SEEDS, AND AVOCADO
Breakfast: 1 cup steel cut oatmeal, six dates, 11/2 T ground flax seeds, 1 cup mixed berries
Snack: One medium banana, 1 oz walnuts
Lunch: Lentil salad made from 3/4 cup cooked lentils, 1/2 cup diced vegetables, and 1/2 lemon blended with water; 1 cup cooked kale; 1/2 cup brown rice; and one medium apple
Snack: 1/3 cup no-oil hummus (with tahini) with 2 cups raw vegetables
Dinner: Power bowl made with 2 cups spinach, 1/4 avocado, 1 cup quinoa, 1/4 cup kidney beans, 1/4 cup corn, six slices of onion, six cherry tomatoes, three carrot strips, and one baked sweet potato
Percent of calories from fat: 22.8%; omega-3 fats: 5.8 g
#3 WITH NUTS, SEEDS, AVOCADO, AND 1 TABLESPOON ADDED OIL
Breakfast: 1 cup steel cut oatmeal, six dates, 11/2 T ground flax seeds, 1 cup mixed berries
Snack: One medium banana, 1 oz walnuts
Lunch: Lentil salad made from 3/4 cup cooked lentils, 1/2 cup diced vegetables, and 1/2 lemon blended with 1 teaspoon olive oil; 1 cup cooked kale; 1/2 cup brown rice; and one medium apple
Snack: 1/3 cup traditional hummus with 2 cups raw vegetables
Dinner: Power bowl made with 2 cups spinach cooked in 1 tsp canola oil, 1/4 avocado, 11/4 cup quinoa, 1/4 cup kidney beans, 1/4 cup corn, six slices of onion, six cherry tomatoes, three carrot strips, and one baked sweet potato
Percent of calories from fat 25%; omega-3 fats: 6.4 g
Source: Analysis conducted with Nutrition Data Systems for Research.
In the first example (#1) of a typical low-fat WFPB menu, the omega-3 fatty acid level is well below the recommended daily intake. The other two examples (#2 and #3) provide sufficient omega-3 levels from added nuts and seeds, and, in the last example, oil. In spite of the added oil (120 kcal/1 T), omega-3 fatty acid and overall fat contributions are similar in both menus. The distinction among menus 1, 2, and 3 is noteworthy because over time insufficient intake of essential fats, particularly omega-3 fats, can lead to fatigue, cognitive issues, skin dryness, heart problems, and poor circulation.25
Cardioprotective Benefits of Nuts, Seeds, and Avocado
There’s widespread and compelling evidence from clinical trials and observational studies showing strong and significant associations between nut intake and CVD and between avocado intake and CVD.26,27 Removing these plant foods from the diet hasn’t been shown to improve health outcomes. In fact, major epidemiologic studies (eg, Nurses’ Health Study, Adventist Health Study, Physicians Health Study) demonstrate an increased risk of premature death with lack of sufficient fats from nuts or seeds in the diet.28-34
What all WFPB proponents agree on is that diets based on predominantly whole plant foods are protective against chronic disease and premature death. While the oil/no-oil controversy persists, the bulk of the evidence supports the inclusion of moderate quantities of fats from whole food sources (eg, nuts, seeds, avocado, and olives) in a WFPB diet. Regardless, dietitians should support their clients’ preferences where reasonable. For example, if clients want to try a very low-fat WFPB diet to control lipids, dietitians should guide them in the most optimal ways.
Brenda Davis, RD, a plant-based diet expert, agrees: “The goal is to optimize absorption of protective dietary components, and adequate amounts of fat help to accomplish this task.” On the subject of oils, Davis says, “While oils are not poisons, getting fat from whole foods naturally increases the nutrient density of the diet while reducing the caloric density.”
Health-supporting diets come in many different styles, particularly with regard to culturally relevant recipes, specific ingredients, and varying macronutrient distributions. When advising clients and patients on healthful WFPB eating, the pros and cons of the different approaches must be juxtaposed with individual goals, health conditions and risk, personal preference, and adherence. While nutrition experts understand the basic tenets of high-quality eating patterns, they can’t say which single dietary pattern is best for health.
“The literature strongly supports a common set of dietary principles for health promotion and the prevention or management of virtually all prevalent conditions in modern societies,” Katz says. “In this context, guidance that places an exaggerated emphasis on any one nutrient or food is ill advised.”
— Dina Aronson, MS, RDN, is director of nutrition programming for Diet ID, a digital dietary assessment and behavior change platform.
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