food eaten - energy exerted = how much fat you're going to gain.
Laboratory is bad/Organic is good
The only reason we've gotten so far as to invent the computer and discuss these things over the internet is precisely the thing that we're talking about - processed foods. These things make it faster for us to find food, rather than spend all day searching for it. Now, are preservatives necessary? Debatable. But other than the preservatives, new techniques in farming and new ways to turn the raw materials into food are the only reason we have technological advances.
Also, pesticides and preservatives? And whenever we find out a chemical used in insect or freshness control is no longer effective or dangerous, we stop using it. There are safe pesticides and preservatives, and don't obsess over the ones that are - science is working hard every day to take those out, and the government wouldn't be as mean as to give you poisonous chemicals.
Food Addiction based on newfangled forms of sugar
Anything can be addictive - even exercising and being healthy (you've seen these people). All you can do is to help the people who have fallen into the trap of addiction, and educate those who haven't already to work to avoid that trap.
High Fructose Corn Syrup
Let's take a look at HFCS, shall we?
What is the main ingredient in High Fructose Corn Syrup? Fructose.
What is fructose? A sugar.
What do we need to have energy? Sugar.
HFCS alone is not a killer - even if you just indulged in sodas and processed foods with cane sugar, you could get fat and sick if you didn't eat it in balance with your activity and main diet. It's more rather, the misuse of food in a lifestyle that doesn't need activity that kills.
Our civilization is going through a period where our primitive, active bodies are competing with our complex, sedentary civilization, and that's the real killer. Go get a jog, and stop complaining about HFCS.