Carbohydrate restriction in Type 2 Diabetes: What does the evidence say?

Some of you may have seen the following NYT Opinion piece trending:
 
http://www.nytimes.com/2016/09/11/opinion/sunday/before-you-spend-26000-on-weight-loss-surgery-do-this.html
 
Especially interesting was the following claim:
 
>>> The diabetes association has yet to acknowledge this sizable body of scientific evidence. Its current guidelines find “no conclusive evidence” to recommend a specific carbohydrate limit. The organization even tells people with diabetes to maintain carbohydrate consumption, so that patients on insulin don’t see their blood sugar fall too low. That condition, known as hypoglycemia, is indeed dangerous, yet it can better be avoided by restricting carbs and eliminating the need for excess insulin in the first place. Encouraging patients with diabetes to eat a high-carb diet is effectively a prescription for ensuring a lifelong dependence on medication. >>>
 
To try to prove their point, Hallberg and Hamby write:
 
>>> At our obesity clinics, we’ve seen hundreds of patients who, after cutting down on carbohydrates, lose weight and get off their medications. One patient in his 50s was a brick worker so impaired by diabetes that he had retired from his job. He came to see one of us last winter, 100 pounds overweight and panicking. He’d been taking insulin prescribed by a doctor who said he would need to take it for the rest of his life. Yet even with insurance coverage, his drugs cost hundreds of dollars a month, which he knew he couldn’t afford, any more than he could bariatric surgery.
 
Instead, we advised him to stop eating most of his meals out of boxes packed with processed flour and grains, replacing them with meat, eggs, nuts and even butter. Within five months, his blood-sugar levels had normalized, and he was back to working part-time. Today, he no longer needs to take insulin. >>>
 
Which was it that was responsible for the change: reducing processed foods, or reducing carbohydrates? These two things changed at the same time. The change may have been for the better, but it doesn’t establish what the authors hope to establish: that a diabetic patient should “first, do low carbs.”
 
To Hallberg and Hamby’s anecdote I might add my own: I once met a patient who, on introducing a single dark leafy green salad each day, reversed their diabetes, had their A1C levels decrease to normal, and could go off of medications.
 
So what about such other diets–those that are not carbohydrate restricted but are intended to help diabetic patients? How do they square off against carbohydrate restriction in Type 2 Diabetes?
 
This question has been addressed in the scientific literature. The answers are different from what Hallberg and Hamby give. A 2015 meta-analysis on the utility of low carbohydrate diets (vs. other diets) in type 2 diabetes found:
 

>>> Recent studies suggest that low carbohydrate diets appear to be safe and effective over the short term, but show no statistical differences from control diets with higher carbohydrate content and cannot be recommended as the default treatment for people with type 2 diabetes. >>>

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4674467/

 
I also really like this excerpt:
 
>>> Interestingly, the carbohydrate debate seems to be based on strong personal opinion and those working in the area tend to cherry-pick the evidence to support their particular view, whether that of low, moderate, or high carbohydrate. Debates about the issue can become very passionate, and it is worth reminding ourselves that “passion in science is an infallible marker of lack of evidence” [3]. >>>
 
That’s a quotation worth remembering.
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