A little while back I listened to this interview with Stephan Guyenet from Whole Health Source blog did with Chris Kresser of The Healthy Skeptic. I highly recommend listening to this, there's lots of info there. Stephan discussed various theories on obesity such as Omega 6's, gut flora, inflammation/immune disorders, etc.
Without trying to put words in Stephan's mouth, my overarching take-away message was that Stephan believes that our bodies have "set points" managed by an "adipostat" located in the hypothalamus. The major hormone involved with the adipostat is leptin. Leptin is secreted by fat cells and circulating levels are associated with one's level of fat mass. The theory is that something throws off the adipostat, and that something leads to leptin resistance of the hypothalamus. When leptin's "stop eating" signal fails to reach the brain, we overeat. Basically each of the possible causes of the obesity epidemic triggers leptin resistance triggers overeating.
OK, so Americans are eating more (150-300 cal/day on average) and getting fatter. Sounds like Calorie Balance theory to me! Gary Taubes in his NYT article stated as much as well, but then went on to write his tome to explain why evidence of Americans eating more was not supportive of Calorie Balance. I guess the mystery is why we overeat and not that we do.
I kind of like Stephan's set point theory -- it makes a lot of sense to me. But it doesn't really counter Calorie Balance, instead he offers explanations as to why we "override" our energy balance. I have to disagree that ELMM is ineffective for weight loss. That is simply not true. It works every time it is tried. Perhaps he means "ineffective" because of difficulties implementing it. But telling people just to cut carbs is no more effective. Despite claims in the New Atkins, I've yet to see any study demonstrating greater success rates and maintenance rates with LC. Yes, there are success stories out there (and I consider myself to be one), but there's no dirth of LC'ers who have regained some or all of their weight back (and I was one of those, twice). To his credit, Stephan notes that LC spontaneously causes most of us to eat less.
As for the calories out, I think Stephan, like Taubes, has gotten sucked into this notion that all exercise does is make you hungry and that everyone who exercises is stopping off for an ice cream smoothie on the way home. Yes, there's some truth to that, but not for everyone. Just because an hour of cardio doesn't offset that smoothie, it's better to have expended those calories than to just have the smoothie. I don't think it is a bad strategy at all to promote exercise of all sorts to at least prevent obesity. While burning 100 or 200 calories may not seem like all that much it does compensate for the fact that on the whole, we expend less energy in our daily lives. Just think remote control, power windows, no microwave, even featherweight vacuums. Also this study demonstrated that moderate exercise increased fat loss independent of dietary composition and did so because the exercisers essentially didn't slow down as much the rest of the day. The added fat loss was attributed to maintaining total daily energy expenditure because the calories actually expended for the exercise itself was compensated for with caloric intake. He does mention a study showing cycling sprints to be more effective for weight loss. Intuitively this sprint vs. long slow cardio seems to counter the Calorie Balance, but as I recall this type of training actually increases energy expenditure for a period following the exercise itself. (I would add that we get less ATP out of glucose under anaerobic conditions so this would also reduce the "in"). Both of these support exercise to increase the "out" side of the equation. Exercising to lose weight is not ineffective if one doesn't ignore the concurrent advice to eat less (or at least not eat more).
None of the obesity epidemic theories dispel the Calorie Balance. Some go to explaining why some may overeat and/or become less active to get the ball rolling towards obesity, but it is physically impossible to accumulate fat mass w/o taking in more energy than is expended. And I'm skeptical that these theories explain why we overate so much in the first place, as much as they may explain why we continue to overeat even after becoming considerably overfat. Many of the proposed culprits (fructose, white wheat flour, veggie oils) have been around in relative abundance since before this epidemic started and they didn't prompt overeating then.