One of my followers asked me to explain the training method I used when I taught Chrome to back up for his dinner. I've always considered myself good at reading the body language of both horses and dogs. I started reading about body language when I was a kid and was fascinated by it. I've been doing it so long now that it's second nature. The easiest way for me to explain what I'm doing is to tell you about 'body blocking' in dog training.
I use body blocking all the time when training my dogs. I use it for teaching a dog to stay out of a particular room or to wait before going through a doorway. Basically I stand in the doorway, facing the dog, legs apart enough to block the route to either side of me and wait the dog out. When I get the behavior I want eg. sitting, laying down or not whining, I step aside, turning away and say 'okay' in a high pitched voice. The square posture facing the dog means 'this is my space and you are not allowed in it' and moving aside while turning away means 'okay you can go through the doorway if you like'. It's basically communicating in the dog's natural body language.
You can also use the body block for a dog who jumps up on people. When the dog starts to jump up you can step into him which knocks him off balance and puts him back on all four or you can turn your back and ignore him. Either one works it just depends on your patience, the size of the dog and what you have in your arms.
With horses the body language is much the same. Square shoulders and a direct gaze means stay back and turning to the side with relaxed posture means they can come closer. To teach the back up using body language you can do it touching them or not. You can put pressure on their chest and wait for them to move away from it, thus removing the pressure and rewarding or you can walk into the horse, raising your arms if needed to create energy and stop when they stop as the reward (or step aside and allow them their dinner). I didn't have to touch Chrome when I taught him to back away from his dinner because we had worked on it before. I basically positioned myself between him and his food (body blocking - don't do this with food aggressive horses) and then I walked toward him. He already knew to back out of my way so all I had to do was reduce the number of steps I took with him and teach a hand and voice cue. Eventually he would back away without me walking toward him. It's pretty simple and works great if you don't have a lot of time to wait for the horse to figure it out on his own. I hope this explained it well. I'm not very good at explaining my techniques because most of what I do is subconscious and/or second nature. Let me know if you have any questions.
With the hope that someone else can explain it better I did some Google searches and here is what I came up with. Just because I agree with some of what they say does not mean I agree with it all. I especially like the last link (which may be where I learned about body blocking, but it's been so long ago I'm not sure). It explains well what I'm trying to say. :D