Low-Carb Diet Has Lasting Benefits in Obese Type 2 Diabetics

In motivated, obese type 2 diabetic patients, a low-carbohydrate diet with some caloric restriction has lasting benefits on body weight and glycemic control, often reducing the need for medication.

Dr. Jorgen Vesti Nielsen and Dr. Eva A. Joensson from Blekingesjukhuset, Karlshamn, previously reported that 16 obese patients with type 2 diabetes who followed a 20% carbohydrate diet achieved significantly better glycemic control and body weight over 6 months than did 15 patients who followed a 55% to 60% carbohydrate diet.

Follow-up data at 22 months for the low-carbohydrate group now shows "stable improvement" of body weight and glycemic control, the investigators report.

At the start of the study, mean body weight was 100.6 kg in the low-carbohydrate group. At 6 months, mean body weight was 89.2 kg and at 22 months it was 92.0 kg (p < 0.001).

"It is significant," the authors note, "that 44% of the patients have had a stable weight or have reduced it further and all but one had a lower weight at 22 months than at the beginning of the study."

Initial HbA1c was 8.0% in the low-carbohydrate group. After 6 and 12 months, HbA1c had improved to 6.6% and 7.0%, respectively, and at 22 months it was still reduced, at 6.9%.

After 6 months on the low-carb diet, 2 of 5 patients using sulfonylurea had discontinued this medication and three were able to lower the dosage. Similarly, 3 of 11 insulin-treated patients discontinued insulin and the mean insulin requirement among 8 had fallen from 60 IU/day to 18 IU/day.

Dr. Nielsen and colleagues also report that seven subjects who switched from the higher-carbohydrate to the low-carbohydrate diet after the initial 6-month observation period also saw improvement in their blood sugar and body weight.

The low-carbohydrate and high-carbohydrate diet contained about the same caloric content (1800 kcal for men and 1600 kcal for women), but the proportions of carbohydrates, protein, and fat were 20%, 30%, and 50%, respectively, for the low-carb diet versus 55-60%, 15%, and 25-30%, respectively, for the higher-carb control diet.

In the low-carb group, the daily quantity of carbohydrates was 80-90 grams and carbohydrates were limited to vegetables and salad. Pasta, potatoes, rice and breakfast cereals were excluded and, instead of ordinary bread, crisp/hard bread was recommended, with each piece containing 3.5 to 8 grams of carbohydrates. The low-carb group was also counseled not to eat between meals.

In contrast, in the higher-carbohydrate diet, whole-grain products were recommended, as were generous helpings of vegetables and several servings of fruit as snacks between meals.

Dr. Nielsen also noted that existing diabetes dietary guidelines are "paradoxical in that they...actually increase blood glucose, cause deterioration of the blood lipids and prevent the wanted weight reduction -- just the opposite of what the physician wants to see in the patients."

When it comes to diet and diabetes, Dr. Nielsen acknowledges that "we know very little and patients should be informed about our lack of knowledge so they can make their own choices. And then they should get our full support in whatever they chose."
Practice Pearls:

· One-year outcomes of a low-carbohydrate diet among patients with type 2 diabetes include a reduced number of hypoglycemic episodes, reduced glycated hemoglobin levels, reduced triglyceride levels, and stable levels of total cholesterol.
· The current study demonstrates that a low-carbohydrate diet may continue to benefit patients with type 2 diabetes for at least 22 months.

Source: Diabetes In Control: Nutr Metab. 2006;3:22