So what, exactly, is the difference between "processed food" and "whole food"?

• Processed foods have parts of the food removed.
• Whole foods have no part of the food removed.

Grain example:

• White rice is rice with the bran layer, and cereal germ removed.
• brown rice is whole-grain rice. Starch, cereal germ, and fibrous bran remain in their whole natural state.

Fruit example:

• Juice is water, sugar, and nutrients extracted from the plant. The fiber is removed.
• In whole fruits, the sugar, fiber, and other nutrients remain in their whole natural state.

Vegetable example:

• Vegetable oil is extracted from the plant. Fiber, protein, calcium, and other nutrients are removed.
• In whole vegetables, the oil, fiber, and other nutrients remain in their whole natural state.

Legume example:

• Pea protein powder is extracted from the plant. Fiber, starches, and some nutrients are removed.
• In whole peas, the protein, starch, fiber, and other nutrients remain in their whole natural state.

Many nutrients are more effective in their whole natural state, compared to the same nutrient in isolation. Fiber slows the absorption of sugars and other nutrients. Nutrients have more time to interact synergistically.

Whole-foods from plants provide all the nutrients that humans need (with the exception of vitamin B12 and D). Counting calories or nutrients is unnecessary.

The whole-food concept provides a simple principle for healthy eating: Eat only whole foods from plants.

Vegan food can contain any amount of processed foods e.g. added sugar and oil. WFPB contains no processed foods.

Vegans that switched to a WFPB diet experienced significant reductions for BMI, blood pressure, and cholesterol.

Evaluation of an Eight-Week Whole-Food Plant-Based Lifestyle Modification Program, 2019
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6770132/

• There were 79 participants, all self-referred from the community, including 24 (30.4%) who were already vegetarian or vegan at baseline… eight-week group program utilizing an ad-libitum whole-food plant-based dietary pattern.
• Participants experienced statistically significant reductions for BMI, blood pressure, and cholesterol.
• When comparing vegetarian or vegan participants to non-vegetarian participants, there were no statistically significant difference in reductions for BMI, blood pressure, or cholesterol.
• Despite the general perception of healthfulness, vegetarian and vegan diets do not exclude processed foods and as a consequence, do not differ much in macronutrient composition from non-vegetarian diets. In the Adventist-Health-Study-2, the percent calories from fat in vegetarian (lacto ovo vegetarian) and vegan (strict vegetarian) diets did not differ significantly from non-vegetarian diets. Strict vegetarians consumed a mean of 29.8% of their calories from fat and lacto ovo vegetarians consumed 33.1% of their calories from fat compared to 35.1% in non-vegetarians. By contrast, the plant-based diets shown to reverse heart disease contained approximately 10% calories from fat. This very low-fat content was achieved by exclusion of added pure fats, processed foods, and high-fat plant foods.

*Equal parts of tomatoes, spinach, lima beans, peas, potatoes
**Equal parts of beef, pork, chicken, whole milk
Source: T. Colin Campbell, Ph.D. and Thomas M. Campbell II, MD. “The China Study.” 2004, CHART 11.2.

Added oil or added fat is oil or fat extracted from plant or animal and added to food.

Added sugar is free sugar added to food.

Free sugars are refined sugars and sugars naturally present in honey, syrups, and fruit juices.

Refined foods are plant foods with fiber and nutrition removed. e.g. white flour, white rice, sugar, protein isolate.

Plant based sometimes means "whole-food plant-based" depending on context.

Processed foods contain added oil, added sugar, or refined foods.

NOVA food processing classification
http://archive.wphna.org/wp-content/uploads/2016/01/WN-2016-7-1-3-28-38-Monteiro-Cannon-Levy-et-al-NOVA.pdf
Minimally processed foods are natural foods altered by processes such as removal of inedible parts, drying, crushing, grinding, fractioning, filtering, roasting, boiling, pasteurisation, refrigeration, freezing, placing in containers, vacuum packaging, or non-alcoholic fermentation. None of these processes adds substances such as salt, sugar, oils or fats to the original food. e.g. whole-wheat flour, natural nut butter, canned vegetables, frozen vegetables, dried fruits.

Whole foods are plant foods that are unprocessed or minimally processed. Whole foods have no part of the food removed.

Vegan foods contain no animal products. It may, or may not, be whole food. Vegan food can contain any amount of processed foods e.g. Oreo cookies are vegan.

Carbohydrates include sugars, starches, celluloses and gums.