This is probably true for non-processed foods, but is definitely NOT true for any kind of processed or restaurant foods. To increase profits, processed, packaged, and served meals have become increasingly less healthy in the past 50 years...either by replacing ingredients with cheaper or longer lasting ones that are coincidentally less healthy (HFCS and trans fats) or by creating larger portion sizes, which take very little additional ingredient cost, but make consumers willing to pay a higher amount for the foods in question. It's not a conspiracy, it's just good economics. Unfortunately, I don't know how aware most people are of the decrease in nutrition and quality in packaged and served goods over the years.
We CAN make the argument that personal responsibility dictates that people not partake in these foods, but it's pretty certain that some people always will, and that the negative nutritional impact of eating those foods on a regular basis has gone up significantly since they were introduced...in other words, what was once a "not so great choice" has become a "very bad choice".
I just read a very interesting book by a former food marketing exec whose argument was, essentially, that the changes to make these processed foods less healthy to make more profits were done without letting customers know...it makes good economic sense for companies to change back to healthier versions, even at a slightly higher ingredient cost, without letting the consumer know (because people believe that "healthy" processed foods taste bad, and don't buy them, and also because healthier processed food options tend to be priced out of low-income grocery budgets...), which will both improve national health AND ensure the food companies have brand loyal consumers with longer lifespans. I wasn't fond of the message that the food industry has to solve the problem, not consumers (I personally think it would have to be BOTH), but the arguments did make sense to a certain degree.