Junk food actually does wear the body down and makes you feel like crap afterwards. I read somewhere one time that when you eat junk food, the body goes into overdrive trying to break down & separate the real nutrients from the processed chemicals in the food. Which causes one to feel worn out, tired, or even sick. In contrast, when you eat healthy food, the body actually energizes itself during the digestion process because it is absorbing mostly nutrients instead processed chemical which in turn you feel energetic, and even lighter.