"it is unlikely he or she will be protein deficient. Physicians in the United States rarely encounter patients who are deficient in protein"
By the same token Dr's in the US constantly encounter patients who are grossly obese so their perceptions of normal may be skewed.
That said I think the main issue is the constant, intake of refined high gl/gi carbohydrates (sugar) breads pasta chips potatoes... without any nutrients or fiber. I think if somebody was to eat a low protein diet with the vast majority of their calories coming from non refined whole foods without needing to rely on post paleo grains and legumes they would do pretty well but that would be allot of eating.
Here are some grains that are not really grains and do not contain gluten or lectins to my knowledge but still this is high caloric density and relatively low nutrient density
http://www.ncbi.nlm.nih.gov/sites/entre ... s=12081852
Again I take this stance because I am extremely sensitive to refined carbs and gain fat /lose muscle when I eat low protein high carb for any period of time. Some people respond well to sugar, but most don't and you can see them all around you struggling to get in and out of their cars. If the low protein diet works for you that is great and you are lucky but if you have been trying to get in shape forever I encourage you to try something like I outlined here http://www.simplefit.org/nutrition.html
I should note that using this program not only did I lose fat and gain muscle but saw drastic improvements in HDL LDL and Triglycerides AKA predictors of syndrome X.
If you do decide to change your diet in any way go to your dr and get those baseline tests: HDL LDL and Triglycerides to recheck.
I know that what I am saying that what I am saying in contrary to conventional wisdom but here is a stack of books by PHD's that helped shape my opinion and reinforced my direct personal experiance
Protein Power lifespan: Michael and Marie Eaded M.D.
Paleo Diet: Loren Cordain, Ph.D.
Lights out: T.S. Whiley Bent Formby PH.D.
Mastering The Zone: DR Sears Barry PH.D.
The base of all those books is evolutionary science not theory that brought us thing like nitrates, olestra, and nitrates. Hard scientific evidence like the fact that fossilized paleo human remains in western Europe indicate that their diet was similar to that of a top level predators like wolves.
Here is tons of free research by Loren Cordain, Ph.D.
Loren Cordain, Ph.D., is widely acknowledged as a leading expert on the diet of our Paleolithic ancestors.