I don't know about you, but when I'm really hungry, my whole world turns upside down. I start to feel jittery, can't form coherent thoughts, often say things I don't mean to say...my whole being starts to shut down.
John 6:53 says, "So Jesus said to them, "Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life in you." (ESV)
Even though Jesus isn't telling those listening to him to literally eat of his flesh and drink his blood, I can see that without consuming Jesus' blood and flesh, our whole being ceases to function in the same way that hunger affects us- "you have no life in you."
To eat of Jesus' body means we acknowledge that His presence is enough to sustain us and His word is sufficient enough to nourish us. When we drink of Jesus' blood, we receive the truth that His sacrifice on the Cross, the spilling of His blood and of His life for us, are enough to cover our sins.
Why must we see Jesus as the "main food group" for our lives? We need Him because the world is only feeding us junk. It boasts that we can be nourished by money, by power, by the love of others, by achievement...you name it. But, when we use these things to feed us, we are nourishing our heart, soul and mind just as sufficiently as a meal of Cheetos and Coca-Cola could. For a moment you are filled, but soon you start to feel that hunger; the aching of your stomach, the shaking of your hands and the edginess that comes when you really just need a wholesome meal.
All this world has to offer will end up starving us. What a gracious and loving Father we have who gives us the true Bread and Wine.