Different foods have widely differing amounts of water within them. The foods that dehydrate best are the ones that have a lot of water to begin with. Obviously, water has no calories, and it means more weight to carry.
Chopped spinach, for example, has a lot of water. I can reduce a whole frozen package in the dehydrator by 10:1 on weight. What I get is some green chips that rehydrate well. So, the dehydrated chips have all of the calories that the whole package had to begin with.
Tomato paste will dehydrate very well, and if you spread it out right, you get a tomato leather. Ziploc bag it. I keep it refrigerated until time for the trip, and then it keeps OK from then on. It rehydrates easily in water or soup. No calories lost. Probably 5:1 weight reduction.
It is easy to buy instant rice, so you don't need to do your own. I cook quinoa and then dehydrate it, and it turns out very good. No calories lost.
You can air dehydrate cooked meat, but the results are mixed (at least for me). Rehydration can be problematic, and sometimes there is a texture problem. So, if I need much in the way of cooked meat for a long trip, I typically purchase more freeze dried.
So, let's say that you are doing a long trip, and you normally need 2 pounds of food per day. If you did a lot of dehydrated veggies and a little freeze dried meat, you can probably cut that down to 1 pound per day or less. Note that you may have to spend more time and fuel rehydrating it in camp, so the victory is not pure.