Gary Taubes blames carbs, especially the refined carbs like wheat and sugar.
Laura Dolson is generally with Taubes on the refined carbs, but she also blames marketing.
As a marketing professor, I find straw men arguments like this patently ridiculous. Marketing is not all powerful; if it were, I would have created a junk product and marketed it to all of you idiots out there, who would have bought it. You wouldn't have a choice; marketing would have forced you to buy it, and I could retire in style to the French Riviera. Unfortunately, life isn't like that. Consumers have brains and can choose to not purchase marketed products. Up to 95% of new products fail, despite massive amounts of marketing. The influence of the home can swamp any marketing campaign. Massive amounts of food industry marketing do not work on me, for example, or the example I set in my family. I have a brain and I choose differently.
Also, does marketing/advertising create food attitudes, or merely reflect already existing attitudes in people? Any competent social scientist will tell you it is very hard to change behavior. While I think marketing can help to create attitudes, it mostly reflects what already exists. Take smoking, for example. Reasons people smoke include parental example/rebellion against parents; peer pressure; stress and anxiety reductions; desire to lose weight, etc. Marketing, though often blamed for smoking (Exhibit A: Joe Camel), is not even mentioned as a factor (I would argue that marketing only informs brand choice, not the decision to smoke). Get real, folks. Marketing is just not as powerful as you would like to believe. It may be a convenient whipping boy, but your belief in the absolute power of marketing is a fantasy.
Kurt Harris blames the Neolithic Agents of Disease, including fructose, wheat, and seed oils.
Stephan Guyenet blames highly palatable food choices for weight gain.
Paul Jaminet blames malnutrition, dietary toxins, and infections for obesity.
Chris Kresser says there is no single cause of or treatment for obesity. Later, he says that modern lifestyle + genetic predisposition = obesity.
What do I believe? I used to believe Gary Taubes, because the solution he proposed worked for me, to a point. Harris, Jaminet, and Kresser are all singing variations of the same tune, so I suppose I am in their camp now. I am following the Perfect Health Diet, though I am stalled at the moment. They seem the most reasonable, the most scientifically based, even though I have criticized science as a justifying principle for belief. But I guess I have to hang my hat somewhere.