At $30/gallon of gas, crude would be…. I dont know, what? $1000/barrel? More? Something like that.
Anyways AN and Breeze are correct that we would see falling levels of obsesity, but not because everyone would be rideing bikes, but because no one could afford to eat(fertalizer, running a tractor, shipping, pesticides, herbacides, all oil as a base ingrediant).
Stores would have to charge like $50 for a loaf of bread. That is a recipe for disaster every time.