On a WFPB WOE (Way of Eating), we try to eat our food in it's most natural, unprocessed form. The best way to eat most all fruits and veggies is raw. The second best way to eat them is fresh cooked. Next in line is frozen, then canned.
If you do most of your shopping in the produce section of your grocery store, then you get an A+. It is best to avoid the center aisles where they house all the boxes, cans, bags, and prepackaged "foods".
But let's be reasonable. Most of us will need to buy items that are somewhat processed: breads, tortillas, condiments, canned beans, spices...But you MUST read the label! Manufacturers are always sneaking in ingredients that are addictive and appeal to your palate and senses. This includes lots of unwanted sugars, sodium and other undesired ingredients! Take canned tomatoes for instance: I assumed all canned tomatoes just contained tomatoes, WRONG! I picked up a can the other day, and it had added sugar! ALWAYS read the label!
Ingredients To Avoid: high fructose corn syrup, corn syrup, hydrogenated or partially hydrogenated oils, all oils (corn, sunflower, olive, canola, soybean, grapeseed...), enriched flour, added sweeteners (aspartame, splenda, sucralose...), hydrolyzed soy protein, soy protein isolate, mono and diglycerydes, and glycerin just to name a few!
The smaller the list of ingredients, the better it is for your body!