Nah, natural is a great way to go, but it is extra work and a lot more expensive. If you read histories of food, you will find a lot of our health problems started popping up with the advent of preservatives and high fructose corn syrup and other nasty things. Michael Pollan's got some great books on the subject.
I agree with you about diets being fads, but the principles of some of these fads are very useful and helpful.
I agree with the timing of the major health problems. There are so many things over the years that have occured around the same time man-made things became commonplace.
My dad pointed out one time that when he was growing up in Carolina in the early 50's, just about everybody drank well water. You didn't have too many places in the country with treated water like we have today. When you look at the timeline for when treated water started becoming more the norm than the exception, it was oddly the same time cancer rates went up 10 fold.
Then when you look at the 70's when everything started making a major push from glass/metal to plastics, autism went from extremely rare to excessively more prevalent than in the past.
There are so many examples of things coinciding with disease rates increasing, that it's hard to pinpoint exactly where it all started. As far as the foods go, you are absolutely right about the preservatives. The only problem I have, is so many people think organics are the answer. The problem with that, is while a lot of it tends to be preservative free, the natural processes they use for a lot of organic foods are more harmful to your body and the environment than the chemical processes for fruits and vegetables were.
I know from working so long in landscaping, that a lot of what people consider chemical and commercial fertilizers, are rarely ever more than iron and nitrogen. Some time in the mid to late 90's, things started making a big switch to natural fertilizers. Most of them consist of pure ****, literally. The problem with feces, is they contain high concentrations of methane and urea, which are both worse for your body and the environment than nitrogen and iron. Since the push for natural fertilizer started, fish kills along waterways has increased excessively, and rates of gout and related disorders has gone up off the charts. Since gout is due to an increase in uric acid levels, which occurs at a rate of 90% in most cases for organic and natural fertilizers, it tends to point to that being a possible link.
Then you have the added problem of preservative free foods having a very shortened shelf life, and it raises the prices of things. If everything went to that method, food prices would be triple what they are now, and they're already too high.
As far as the diets go, I have asked three doctors what diet they recommend. They seem to all have the same response - don't do any diets, because the main benefit is weight loss, but you give up so much more that you need in exchange, which leads to health problems.
You have a lot of diets that tell you to cut out sugar. When you do that, since your body requires sugar, it starts to try taking it by breaking down every carb you take in. When you get to the point where your body needs more than you're taking in, your body robs the reserves, which are in your organs, and that's no good. Then you have the people that do the Atkins thing, which long term will lead to ketosis, and the possibility of kidney and liver failure. Then you have high protein diets that put stress on your heart and liver. It seems to me from a lot of research I've done on various diets, that the risks always seem to heavily outweigh the benefits.
The simple fact is, if we could all afford to eat preservative free food, and only take in natural sugars, and eat lean meats and get off our asses and work out once in a while, we'd be just fine. The paleo diet seems like a decent start to that idea, but it doesn't take into account the things your body needs to function, and the levels that you need of them. A perfect example being the whole no sodium approach. I promise you that having no sodium in your diet will absolutely 100% kill you. Your body needs sodium because it is an important electrolyte, and if you aren't taking any in, you are slowly but surely committing suicide.
My point is basically don't believe the hype of any diet, because they all exist to make somebody money. Instead, do some research on human biology and what makes us function, what harms us, and base your diet off of that. there isn't a diet I've seen in my life that doesn't tell you to completely cut out something you need to survive.