Jesus was dead serious when he told the people to eat his flesh. He said it like it wasn't figurative in any way. He is really the Bread of Life, and as Bread we have to really eat him. Bread is food, after all, designed to be eaten. And eating him is the only way to have eternal life. Watch this:
For my flesh is real food and my blood is real drink. 56 Whoever eats my flesh and drinks my blood remains in me, and I in them. [John 6]
Before that, he said:
Unless you eat the flesh of the Son of Man and drink his blood, you have no life in you.
His flesh is real food. It's literal. But then, it's literal in a spiritual way. You really have to "eat him" in the spirit. I know smart Alecks will tell me it's figurative. But no, I believe it's literal, but in a spiritual sense, like how we true believers can see Jesus and the Holy Spirit, as Jesus said in John 14, which we'd tackle in another issue. The world cannot see him but we believers can. See? And that's not figurative, symbolic, metaphorical, allegorical or anything like that. It's real, in a spiritual sense.
Anyway, Jesus is the Bread of Life, and he added that the real Manna that came down from heaven was him. It wasn't the manna that Moses gave them. So, he used this context to show himself the Bread of Life. Brilliant. In Moses' time, the Israelites who fled from Egypt crossed the desert from Salim to the Desert of Sin and found themselves with no food to eat there. They grumbled. So God decided to provide them with a unique bread that rained down from heaven in flake form.
Manna came when they were in the desert and when there was nothing else to eat there (no choice but to eat the manna. Beautiful!). Jesus, the Bread, comes to you in your wilderness experience, in a life crisis, especially when you discover that there's nothing really worth eating or edible there (in fact, anywhere in this world) except the Manna from heaven. Without this crisic experience and realization, you can never "eat" Jesus as your Bread of Life. Many folks came to "know" Jesus as Savior as they were invited to church, given special treatment there, became involved in church and enjoyed the programs and activities and later given major roles and positions. Everything in convenience. That's good, but without life crisis, it will never lead to truly realizing Jesus as your Bread of Life.
You need the wilderness experience. You need to get out of Egypt and be purified in the wilderness as Moses was. From being prince in Egypt he settled to being a mere lowly, faceless shepherd in a strange country. You lose a lot of precious things and possessions and comfort in the wilderness. You lose your ego, importance and position. You become settled in the background, sometimes, in a dimly lit corner there where you're a nobody. Where you're insignificant. Believe me, you need that. It's more important than all your achievements and trophies. There, you are stripped to bare essentials---and find that nothing has meaning in this world. Only Jesus and his heaven means a lot.
Set your hearts on things above, where Christ is, seated at the right hand of God. 2 Set your minds on things above, not on earthly things. [Colossians 3]
It's like this---as you deepen in your knowledge of Jesus, you realize this world and everything in it stink. You lose interest in them. Nothing in this world makes sense anymore. Before, you found a lot of good food dishes in it (gimmicks, fun, career, entertainment, achievements, success, titles, degrees, positions, riches, fame, etc.) But after getting a taste of this unique Bread, all others became stale. Even poison. You want nothing but Jesus. You feed on him.
Before long, your friends (sometimes even church and family) begin to find you odd and reject you. They find it strange (and even stupid) why you're so contented with just having Jesus, having an appetite for him alone, and not even trying the world's desserts. At first you starve because you're left with nothing. You're abandoned. They hate you. Then you find that only Jesus is reliable and trustworthy. You learn to run to him each time, and then later crave for him like you do your favorite food. You discover that the only real food in this world is Jesus. It's when you don't just read the bible---you eat the Word of God. You eat Jesus.
The one who feeds on me will live because of me. 
If you eat Jesus, you live the Jesus LIFE. You begin to have His mind, taste, preferences, priorities, ways, culture, etc. And you begin to reject anything of this world, even a small trace of it. So, once you begin to see how worldly the modern church is, you get disappointed and start looking for the genuine church of Jesus Christ, without spot or wrinkle or any other blemish---holy and pure. You realize what LIFE really is. You enjoy that LIFE.
Well, others will also discover Jesus as Bread of Life for a while and eat him now and then. But they won't last. You know the story of the Sower---how the sower sowed seeds which fell on different grounds. A lot of the seeds sprouted immediately but came to nothing. Likewise, pretty soon, these folks who ate Jesus as the Bread will get fed up from eating nothing but Jesus and reject anything about him. Something like:
“If only we had meat to eat! 5 We remember the fish we ate in Egypt at no cost—also the cucumbers, melons, leeks, onions and garlic. 6 But now we have lost our appetite; we never see anything but this manna!” [Numbers 11]
I see this often in the modern church. Christians doing everything in church except deepening in their knowledge and experience of Jesus through his Word and seriously living out his Word daily, living his very LIFE and character. All they want is the religion. Even pastors preach nothing but inspirational sermons and ministry strategies---to prod people to be active in getting more people to church and up the membership and income. I seldom see young people in church seriously interested in the Old Testament. Sometimes, they're even lazy with the New Testament.
Worse, they copy what they see works effectively in the world and do that in their church. They're not led by the Holy Spirit. All they want is activities, and their pastors feed them that, too. They think their members grow spiritually with sermons, Sunday school, bible studies, music and singing, concerts, seminars and ministry. Nobody talks much about Jesus in depth and up close and especially about eating him. Truth is, if we always prioritize eating him, all other things will be added unto us, especially evangelism and church planting.
And I, when I am lifted up from the earth, will draw all people to myself. [John 12.32]
If you do not change diet and really feed on Jesus, the thoughts and joys of "Egypt" (the world) remains with you and you easily revert back to it. You still easily get attracted by the world and you think it's normal. You think it's okay to mix God, ministry and the world. A lot of pastors copy from the world anything they find effective for their ministry and think it smart.
If you eat just bits of Jesus now and then or serve him as main Course only periodically in your church, you have not developed a taste for Jesus yet. You just try tasting a piece of him now and then. If you haven't developed a taste for Jesus, you will easily be lured to other cuisines and later loath the Manna from heaven. Remember the Passover lamb? You and your family had to eat the whole lamb. No leftovers. You have to eat Jesus wholly.