Your favorite potato chips contain carbohydrates, protein, and fat—three of the four main types of organic molecules in cells. If you must obtain these molecules from your diet, why are chips considered a junk food?
In general, junk foods like chips and candy are high in fat or sugar (or both) but low in protein and complex carbohydrates.
They also typically have few vitamins and minerals. Junk foods therefore are high in calories but deliver little nutritional value.
Many junk foods also contain chemical additives. One common ingredient in packaged cookies, pies, and other baked goods is partially hydrogenated vegetable oil, a type of chemically processed fat. Partial hydrogenation causes fats to remain solid at room temperature; it also produces trans fats, which have been linked to several diseases.
Some junk foods also contain artificial colors, flavor enhancers, artificial flavors, and preservatives that make food look or taste more appealing without adding nutritional value. One example is monosodium glutamate (MSG). This chemical consists of an amino acid and a sodium atom connected by an ionic bond. It enhances the flavor of many packaged snacks and fast foods, imparting a savory taste. Moreover, preservatives such as BHA and BHT increase the shelf life of many junk foods. These chemicals prevent oxygen from interacting with fat, so it takes longer for the food to become stale. Potato chips, pizza, fries, candy bars, snack cakes, and other junk foods are hard to resist because they tap into our desire to eat sweet, salty, and fatty foods. These snacks are tasty, appealing, easily available, and often cheap. But for a more nutritious diet, reach for whole grains, fresh fruits, and vegetables instead.