If you\u2019ve read any nutritional advice lately, you\u2019ve probably encountered one hard-and-fast rule: Avoid processed foods. But what does \u201cprocessed\u201d mean? On one level, anything humans do to food \u2014 slicing fruit, cooking beans, fermenting cabbage into sauerkraut \u2014 constitutes processing. It\u2019s obviously silly to say that an apple eaten whole is healthy, while the same apple sliced isn\u2019t. And even if you can call the ingredients \u201cprocessed,\u201d there\u2019s nothing unhealthy about a good, crusty sourdough bread made with whole wheat flour or cold-pressed extra virgin olive oil. Why should a diet forbid them? Another school of thought says that if cooking and chopping are benign and even healthful, then any other form of processing is good, too. But what rational person would say that a roasted chicken is nutritionally equivalent to a Chicken McNugget? Here\u2019s what you really need to avoid: ultra-processed fare. Ultra-processed foods are made with ingredients not normally found in a household kitchen, such as artificial flavors, colors, and emulsifiers. It\u2019s a simple but logical distinction. A smoothie made from fruit and yogurt is processed in the ordinary way. But if you add artificial flavoring, Red Dye #40, and high fructose corn syrup, then it\u2019s ultra-processed. A recent study found that over half of the calories Americans eat come from these ultra-processed foods. Yet some of the confusion over the difference may lead to calls for people to avoid all processed foods. For example, a fruit salad is an undeniably healthy snack. But if you didn\u2019t make it yourself, it may have been treated with a preservative. Likewise, humans have eaten oils for millennia. But they\u2019ve only recently begun extracting it with solvents like hexane. If you buy a bottle of vegetable oil at the store \u2014 or a dish fried in a vat of oil at a restaurant \u2014 do you know what you\u2019re getting? It can be hard to know where to draw the line. And it\u2019s getting more difficult as ultra-processed foods warp people\u2019s taste buds. Food journalist Mark Schatzker, author of The Dorito Effect: The Surprising New Truth About Food and Flavor, made another prescient observation: As ultra-processed foods become ever more irresistible, some of the better alternatives have become less tasty. It\u2019s true. Factory farms have bred broiler chickens to grow to maturity at five weeks, before they develop flavor. And vegetable shippers have selected tomatoes that are big, red, round, and ship well \u2014 but taste like styrofoam. Can you blame eaters for turning away from them? We don\u2019t need restrictive regimens banning us from cooking, slicing, steaming, and fermenting to shape up our diets. And you don\u2019t have to buy everything you eat at farmers\u2019 markets or grow it yourself, as tasty as that might be. But it\u2019s safe to say that cutting back on Twinkies, Peeps, Flamin\u2019 Hot Cheetos, Easy Mac, and other ultra-processed foods will do the trick. OtherWords columnist Jill Richardson is the author of Recipe for America: Why Our Food System Is Broken and What We Can Do to Fix It.