You can make vegetable protein more complete by eating more than one kind at the same time. For example, eating corn and beans. Simple carbohydrates, or sugars, give the body energy, but little else in nutrients. They also have a lot of calories. It is best to limit them.
Complex carbohydrates are an excellent source of energy and other nutrients.
They also provide fiber. Complex carbohydrates give you energy, provide vitamins and minerals and fiber. This is the fat on your body. If you eat more calories than you need, you will make too much body fat. This is fat that you eat.