While not all food that comes from a package is unhealthy, eating a diet full of heavily processed fare is linked to a number of health concerns. Reading the labels on processed foods is especially important, as many are missing important nutrients or have some unsavory added ingredients. In some cases, however, lightly processed foods may be preferable to their fresh counterparts.

Processing occurs any time you alter a food's original form. This includes cooking, freezing, chopping, fortifying and fermenting. Lightly processed foods such as frozen, unseasoned vegetables don't pose any health concerns -- in fact, freezing produce preserves some of the nutrient content. That said, heavily processed foods laden with fat, salt and sugar -- such as deli meats, cheesy crackers and frozen pizza -- may cause health problems when consumed regularly. In addition, processing techniques such as canning, dehydrating and cooking may cause foods to lose vitamin C, B vitamins and other important nutrients.

During refined-grain processing, food makers remove the bran and germ of the grain, leaving only the starchy endosperm. The removed portions are high in fiber, while the endosperm is not. Because fiber aids in digestion, a diet rich in refined grains from white bread, white rice and white pasta may lead to constipation. In addition, low-fiber diets may be linked to diverticulosis, a condition in which small pouches form in the colon. In some cases, these pouches become infected and inflamed, requiring medical treatment. For healthy digestion, choose whole-wheat bread, brown rice and oatmeal instead of refined grains.

Most Americans consume far more sodium than they need, mainly from processed and restaurant-prepared foods. High-sodium diets are linked to high blood pressure, possibly increasing the risk of heart disease and stroke. Most people should get no more than 2,300 milligrams of sodium per day, and those with higher risk of cardiovascular disease should get no more than 1,500 milligrams of sodium per day. To help curb sodium intake, look for the term "low-sodium" when choosing processed foods.

Research shows that diets rich in processed meats, refined grains and sugar-sweetened foods are more likely to lead to obesity than diets based on whole grains, fruits and vegetables, according to Harvard School of Public Health. Obesity increases the risk of heart attack, stroke, arthritis, Type 2 diabetes and certain types of cancer. Therefore, avoiding refined and heavily processed foods may help you maintain a healthy weight and possibly reduce your risk of chronic disease.