Two diets - one severely restricting carbohydrate intake but with no limit on calories, and the other emphasizing low-glycemic carbohydrates and low calories - allowed high percentages of obese type 2 patients in a university study to reduce or even eliminate their diabetes medications (95.2 percent of the patients on the extreme low-carb diet and 62.1 percent of the patients on the low-glycemic diet).

Researchers at Duke University Medical Center assigned 84 patients to one of two diets over a 24-week period. The first, called a "ketogenic diet," restricted carbohydrate intake to 20 or fewer grams per day, a radical amount compared to the ADA's recommended daily minimum of 130 grams and even to low-carb advocate Dr. Richard K. Bernstein's 30-grams-per-day recommendation.

In a ketogenic diet, the body is forced to use fat to provide energy, a process that produces a metabolic product called ketones. 

The other diet stressed the consumption of low-glycemic foods, which are absorbed slowly by the body and do not cause spikes in blood sugar levels. The diet also severely restricted daily caloric intake to 500 calories. That drastically low number came about because the study was designed to test intense approaches to treating obese people with diabetes whose previous forms of diet and management had not worked.

Although both diets produced substantial improvements in patients, the ketogenic diet was clearly more effective. While Duke researchers did not always spell out the actual measurements produced by each diet, they said that the ketogenic group enjoyed lowered A1cs, greater weight loss, and a larger increase in "good" cholesterol compared to the low-glycemic group. 

The medical center quoted Dr. Eric C. Westman, who led the study, as saying, "It's simple. If you cut out the carbohydrates, your blood sugar goes down and you lose weight, which lowers your blood sugar even further. It's a one-two punch." In fact, reports Reuters, the Duke researchers concluded that "lifestyle modification using low carbohydrate interventions is effective for improving and reversing type 2 diabetes."