The world is a paradox

That fact that we live in a paradoxical society is not new.  Much of the medical research released to the public is contradictory.  A lot of the advice offered to people is in stark contrast to what they read the previous year, month, week, and even day.  Because of this, it's no surprise to me that food advertisements often glorify and promote sugary, salt-filled options while society at large is told to "eat heathy", "increase fruit and vegetable consumption" and "watch sodium intake."  
 I find myself angered when I read articles that allude to this paradox such as the one found on the Science Daily website (http://www.sciencedaily.com/releases/2009/01/0901192104440.htm).  People do have the ability to express agency, and "bad" foods are okay sometimes.  Of course, the creators of these "bad" foods have ample amounts of money to advertise where farmers do not, but I believe the public is aware of this fact.  How much of an effect does advertising really have on society? Perhaps I am completely naive, but aren't people able to form their own ideas, thoughts, and opinions on whether to buy products or not? And what's wrong with buying the occasional bag of chips or box of candy? Okay, perhaps magazines should be asked to cut back on the number of advertisements for "unhealthy" foods.  But would that help?  Would that change the way we eat? Here's the other paradox: we live in an overweight nation.  Almost all advertisements feature uber thin models. It is clear that the abundance of underweight models in advertising does not encourage the attainment of an underweight status in most individuals.  So do food advertisements really work to encourage the consumption of "unhealthy" foods? Which has more influence, advertisements or the messages and articles we read about consuming a "healthy" diet? What is the real relationship between advertising and behaviour? I'm so curious to know. How much of an effect does advertising have on the way we live? Would seeing ads with "healthy" food options increase the consumption of "healthy" foods? Would advertising the consumption of fruits, vegetables, and low-fat dairy and grains increase the quality of Canadians' diets? This is something I would really love to learn more about.