I found this excerpt about the difference of eating foods that have high nutritional value versus low and what this means in terms of calorie intake. The article (from Calorie Count) says:

Vegetables are loaded with fiber, which automatically lowers the calorie density of your food because your body can’t digest it entirely. When South Korean researchers fed women an equal volume of either plain rice or rice with added vegetables, those who feasted on the veggie-filled rice downed 41 percent fewer calories and felt more satisfied afterwards.

This means that you can eat LESS of vegetables and get the same feeling of being full as you would get if you ate MORE rice. Rice has more calories, so you are ingesting more calories with rice than with vegetables. You can therefore live on less calories a day if you eat the right kinds of foods, with in turn helps you to lose weight more easily!