The goal of fasting is to let go of the control that food has on our bodies and our souls. But if we spend so much time and energy reading every label, obsessing over the ingredients of every item we purchase or consume, then food is still controlling us. Just in a slightly different way. And then we misunderstand the point of fasting in the first place! As the saying goes: "Everything in moderation." When you can, try your best to adhere to the rules of the fast. In times when you cannot, that is okay! There must be balance, lest our fasting become the fasting of the Pharisees, which our Lord Himself condemns.