You can eat at fast-food restaurants, purchase snacks at convenience stores and grab quick meals out of vending machines and still have a healthy diet, says Elizabeth Applegate, a lecturer in nutrition and a fitness expert at UC Davis. She suggests selecting foods that are high in carbohydrates and low in fat. Pretzels are a better choice than potato chips, and fruit juices are better than sodas. "People should be eating five to six times a day and concentrating on smaller, more nutritious meals," says Applegate. "A good guide in choosing a low-fat diet is to choose foods that do not contain more than three grams of fat for every 100 calories." In fast-food restaurants, she says, the general rule of thumb is that the less expensive selections are usually more nutritious. By being more selective and aware of food labels people learn the concept of fat budgeting -- how to include an appropriate amount of fat in the diet based on total energy expenditure. Applegate is the author of a just-completed book on nutrition titled "Power Foods."