Some foods -- such as celery -- can be eaten without much concern about weight gain. These foods are generally either very low in calories, or the available calories are quite complex and provide fewer effective calories, or both. Other foods that are generally so low in calories that you can eat them without concern include most stalk vegetables (broccoli, asparagus, and cauliflower), as well as other vegetables that are typically served as appetizers (peppers, carrots, cucumbers, and mushrooms). Additionally, these foods are high in the complex carbohydrates called fiber. High-fiber foods, including cereals (grains, etc.), have also been linked to reductions in the risk for cardiovascular disease. Most vegetables in the legume family, which includes beans and peas, contain useful amounts of protein, but some also contain more calories as vegetable fats and are not as useful for unlimited consumption.
In addition to raw or steamed vegetables that can be eaten in relatively large amounts without substantially contributing to your effective calorie count, good snacking choices include sugar-free flavored gelatins (which can be combined with fat-free whipped topping for a guilt-free snack or dessert), fat-free popcorn, and rice cakes. Tea, coffee, broths, and artificially sweetened beverages are also on the list, and sugar- and fat-free hot chocolate is a good treat for people who like chocolate.
Foods that are high in protein and low in fat and simple include shrimp, crab, some fish, and lean meats (chicken, venison, ostrich, bison, certain cuts of beef, and most wild game). Although relatively high in fat content, the high proportion of protein in salmon makes it a good example of a relatively high-calorie food that is acceptable, because of the energy needed to break down the protein and beneficial fats. Some fats are essential, and deep sea fish is an excellent choice; it is also one of the few natural sources of vitamin D.