It's up to us as individuals to find out what the best, most healthful way to eat is and then do it. Don't wait until your pastor tells you to change. He might not ever do it. But God has made it plain in His Word. I've had people tell me that God doesn't care what we eat, so long as we are moderate, so long as we don't get too fat.
Most disease takes long enough to develop that the connection to diet is lost or overlooked.
No, because He has a plan for your life, and you need to be fit and full of energy to perform it. And you need to be alive. You can't serve the Lord on the earth from an early grave. You won't do all you could for Christ from your sickbed or sleeping off the sugar blues. You won't serve the Lord to full capacity if you're too ashamed of yourself to minister to others.