Low-carb diet improved diabetes control, but effects didn't last

Patients with type 2 diabetes randomized to a low-carb, high-fat diet for six months showed more improvement in HbA1c level than those assigned to a low-fat, high-carb diet, a Danish trial found.

A low-carbohydrate, high-fat diet improved glycemic control and weight loss in patients with type 2 diabetes, but the effects were not sustained after the dietary intervention stopped, a trial found.

The study randomized 165 Danish patients with type 2 diabetes (mean age, 56 years; 58% women) to one of two calorie-unrestricted diets for six months: a low-carb, high-fat diet with 50% to 60% of calories from fat, less than 20% carbohydrates, and 25% to 30% protein or a high-carb, low-fat diet with 50% to 60% carbohydrates, 20% to 30% fats, and 20% to 25% protein. Follow-up continued for three months after the diet period. Results were published by Annals of Internal Medicine on Dec. 13, 2022.

Patients assigned to the low-carb, high-fat diet had significantly greater improvements in HbA1c level (mean difference in change, 0.59%; 95% CI, 0.87% to 0.30%) and lost more weight (mean difference in change, 3.8 kg; 95% CI, 6.2 to 1.4 kg) compared to those assigned to the high-carb, low-fat diet. Both groups had improvements in levels of high-density lipoprotein cholesterol and triglycerides at six months. Changes in low-density lipoprotein (LDL) cholesterol levels were less favorable in the low-carb group, and there was no statistically significant difference between groups in nonalcoholic fatty liver disease. Three months after the diets ended, the improvements in glycemic measures were no longer observed.

The study authors concluded that the beneficial effects of the low-carb, high-fat diet outweighed the minor increase in LDL cholesterol levels seen with it but added that the “recidivism noted 3 months postintervention suggests that long-term adherence to the [low-carbohydrate, high-fat] diet as a lifestyle change may be needed to sustain improvement.” Limitations include that it was an open-label trial with self-reported adherence that was not intended to achieve weight loss.