This is a huge one for me. You can do your own research and find out that basically refined white sugar and refined white flour are poison. They are so high on the glycemic index that they create a huge blood sugar spike and through all of our endocrine system (hormones that regulate all of your internal functions and equilibrium) into chaos. No wonder we all feel like crap all the time. These are are both, at least for me, the most important and most difficult to change.
Sugar. When we start talking about eliminating sugar from our diet everyone's first thought is to what we are going to replace it with. There are some options, but if you are thinking this way I think you are setting yourself up for failure. We are way too dependent on sweets in the US (and I am the worst) and what we call a sweet tooth is actually an addiction, where our bodies will require more and more to be satisfied. It may be like getting off drugs for some people, but we have to break our addiction before we do anything else. In the end most of your sugars should come from plain raw fruit, with a little bit from whole cane products for a treat. I can go into a choice by choice explanation of what's wrong with other options, but you can find it a hundred other places. Basically anything that is modified using high heat or enzymes is something your body doesn't need. Honey is the most popular substitute, but it is 96% simple sugars, so while it is a natural product it will still cause your blood sugar to spike and fall.
Grains. Most of us know we should be eating whole grains instead of white flour, but we probably aren't very good at it, especially for deserts or when eating out. What we also don't know is that whole grains come with their own set of problems. In the Bran of the grain are "anti-nutrients" which keep us from getting the whole benefit from this food. The solution is to soak or sprout flours (I hadn't ever heard of this either) like people have been doing for centuries. This turns the grain into something like a vegetable which our body digests much more easily. There is a wealth of information on how to do this yourself, or if you can afford it there are grain products available (like Ezekiel Bread) that are made with sprouted grains. However for most of us, this is going to be a really long process of transition and experimenting. In the mean time please eat whole grains. They are still so much better for you than white. I think the biggest part of this whole type of diet is to quit compromising on the things we already know. We can't start trying unusual things until we are willing to commit to what we already know is best for us, and make use of the good nutrition that is already available to us.
Did I mention that many people who have trouble digesting grains, and resultant health conditions like Celiac Disease, often have no trouble eating sprouted grains?! This is enough good news to convince me.