Re - the Paleo Diet. I agree that it's not sustainable but that's not anything I can solve. I'm lucky enough to be able to afford anything I want to eat so I'm going to eat what I consider to be the best food. Of course, it's quite possible to look at it from the viewpoint of our population being unsustainable, rather than our diet being unsustainable. Like I've said many times, I'm interested in optimal nutrition for me, not how to feed the world. That's a misuse of the word 'decimate' of course; we'd need to reduce it by much more than 10%.
Diabetes and the J diet: I've been agreeing with the general idea that the traditional J diet seems to get better results than most but there are a gazillion things going on which make it tough to single out what is causing those results. The traditional J diet includes things like deep-fried pork cutlets in eggs, on a bed of rice. In other words, a nightmare from the standpoint of almost any diet. but it is perhaps being counteracted by the relatively huge amount of incredibly nutritious sea vegetables (konbu, seaweed etc). Like I said earlier, sheer caloric restriction may have had an awful lot to do with the lifespans - there is a lot of info to suggest that just eating less food, no matter of what kind, can have a very significant impact on lifespans. And Japanese cooking is renowned for the tininess of its portions, which probably stems from a historical lack of arable land for farming. There have also been significant periods of famine in modern history, thanks to the wars.
Are we going to have to start fighting about heart disease now? Something which was practically unknown until modern times? Maybe you're going to suggest that humans only started eating meat since McDonalds opened its doors?
If there's a link between red meat and heart disease, which has not been demonstrated outside of observational studies that I'm aware of, I'm of the opinion that it's due to the poor quality of most meats right now, not because of anything intrinsically wrong with animal protein. Industrially-farmed meats are a toxic mess with very little nutritional value, so it makes plenty of sense to avoid them. Again, though, I can afford to seek out organic, grass-fed beef, organic eggs etc. Given my excellent bloodwork since i've made these changes I'm perfectly happy to continue the experiment, since no-one in academia is doing it for me. I've never suggested anything along the lines of an 80% protein diet though, that's truly absurd. Adequate protein for recovery, preferably organic, grass-fed meat, organic eggs, wild game, good fats, and carbs from non-starchy, nutritious vegetables.
If you want a study to chew over, try the New England Journal of Medicine. 322 participants, 2 yrs, 95% adherence.
I find it frustrating, as the goal is focused on weight loss, not overall health. Still, the indicators for long-time health improved best on low-carb. The other diets involve calorie restriction whereas those on low-carb were unrestricted in that regard. Nevertheless, those on low-carb lost more weight. I wish they'd do one on HEALTHY people (i.e. not obese, because anyone who starts obese and gets thin is going to see improved health markers across the board no matter how they get there, IMHO).
http://www.nejm.org/doi/full/10.1056/NEJMoa0708681