I've read Taubes work on the carbohydrate hypothesis, Guyenet on food reward, and Becker on the Hypothalmic Hypothesis. My background is organic chemistry, not endocrinology or biochemistry, so much of the deep theory is a bit much for me.
Recent work in rats and humans has shown that Roux-en-Y Gastric Bypass rapidly resolves type 2 diabetes much faster than the corresponding drop in weight, proving that it's not caused by solely weight loss.
How does this factor in to how we think about T2D and obesity?
Here are a couple of papers that suggest weight loss surgery is not necessarily the panacea wrt diabetes:
Roux-en-Y is a pretty drastic surgery. It may or may not resolve obesity and/or diabetes. But it is a good bet to set someone up down the road for critical nutritional deficiencies. It makes me sad that it's something people feel compelled to do.
I think there's something about the incretins -- like GLP-1 -- that play a role in insulin signaling and may mimic insulin. The theory goes something like: more rapid delivery/more "bolus" delivery of nutrients to the ileum restores GLP-1 secretion that is impaired in diabetics.
I had just found a paper where GBP reversed diabetes in a non-obese animal model: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1356425/
A non-surgical option there would be Byetta or Victoza -- both GLP-1 mimetics. Byetta produces weight loss, especially in the most obese. I would think this would be worth a shot before GBP for sure.
Based on overall reading, it seems that weight loss--regardless of the foods eaten--will improve health numbers at least temporarily. There are definitely a number of ways to lose, with varying possibilities of sustainability for the longer term.
In my opinion, it's more a question of how the individual will maintain the lowered weight or continue the weight loss without deterioration in health: losing muscle vs. fat, suffering a return of binge eating, etc.
Starvation diets, extreme diets that limit the food list too much risk a kickback reaction at some point or an inability to stick with the plan long enough to achieve your goals.
The above comments pertain mostly to people trying to lose weight. For those already at a good weight but seeking improved or continued good health, the question remains, what are you willing to eat for the rest of your life to maximize your health?
Disney Obesity Exhibit 6 Answers