Have you ever seen the movie Nacho Libre? Well there is a line in the movie where Nacho says that the eagle eggs didn't give him any nutrients. This reminded me of something I learned a while ago and relearned today... Nutrient Density! This means that you are measuring the nutrients provided in a food per kcalorie of that food, or in other words, how much nutritional value you are getting from the food you are eating.
1/2 cup of cooked broccoli is considered to have a high nutrient density because it is high in nutrients relative to its caloric value. In comparison a chocolate cupcake with frosting has many more calories and few nutrients making it a low nutrient density. These foods are sometimes referred to as empty calorie foods because they aren't providing you with the nutrients that you need.
Fruits and Veggies are going to have a high nutrient density whereas fast food and candy will have a low nutrient density. You can choose what you want to eat. I am not saying never to eat "junk food" again--I actually just put a dove dark chocolate in my mouth :)--I am just hoping that you become aware of what you put in your body.
Challenge: Write down everything that you eat for one day and go to choosemyplate.org and see how many empty calories you ate that day. Then figure out what you can improve on. Good luck!