Vegetables are generally low in calories and form the basis of a healthy diet. For example, a bowl of spinach contains only 7 calories, while a medium-sized cucumber contains about 16 calories. Vegetables such as broccoli, carrots and peppers are also low in calories, but are rich in vitamins, minerals and fiber. Thanks to this low-calorie content, vegetables help to keep you full, help with weight control and support overall health. For a healthy diet, vegetables should be an important part of your meals.