How does a low-carbohydrate diet compare to a high-carbohydrate diet for the management of Type 2 diabetes?

This study compared the effects of a low-carbohydrate versus a high-carbohydrate diet on glycemic control and heart disease risk in obese adults with type 2 diabetes. This study concluded that both diets helped reduce body weight, HbA1c levels, and fasting blood glucose levels. However, the low-carbohydrate diet led to greater improvements in heart disease risk factors and diabetes medication requirements.

Dietary changes are a key lifestyle intervention for long-term diabetes management. Reducing reliance on anti-diabetes medications can help reduce treatment costs and drug-related side effects. Specifically, diets with very low carbohydrate and high fat intake have become a popular intervention. Because this type of diet replaces carbohydrates with fats, saturated fat intake is often increased. This can increase LDL cholesterol, which is a main risk factor for heart disease.

Previous studies have investigated the outcomes associated with low-carbohydrate (LC) diets with mixed results. Few studies have investigated the long-term effects of this type of diet on glycemic control and heart disease risk in type 2 diabetes.

This study involved 115 obese adults with type 2 diabetes randomly assigned to either a low-carbohydrate (LC) diet (49.5%) or a high-carbohydrate (HC) diet (50.4%). The LC diet was high in unsaturated fats and low in saturated fats, while the HC diet was low-fat. Participants also had supervised exercise for 3 hours per week. 71% (LC) and 65% (HC) of participants completed the study. Follow-up occurred at 24 weeks and at the end of the study period (1 year).

HbA1c (average blood glucose over 3 months) levels decreased by 1.0% in both diet groups. Fasting blood glucose (blood glucose after 8 hours of fasting) decreased by 0.7 units (LC) and 1.5 units (HC). These differences were not statistically significant.

52% (LC) and 21% (HC) of participants reduced their diabetes medications by at least 20%. 29% (LC) and 18% (HC) of participants reduced their diabetes medications by at least 50%. These differences were statistically significant.

An average of 9.8 kg (LC) and 10.1 kg (HC) of body weight were lost, with an overall reduction of 9.1%. The LC diet was associated with improved triglyceride (type of fat in the blood) and HDL ("good") cholesterol levels. Changes in blood pressure and LDL ("bad") cholesterol levels were not significantly different between the groups.

6.9% (LC) and 11.3% (HC) of participants reported muscle-related issues associated with the exercise training. 1.7% (LC) and 0.8% (HC) reported constipation and intestinal wall infection (diverticulitis). 0.8% (HC) reported bacteria-infected ulcers in the throat. 0.8% (LC) had a hypoglycemia (low blood sugar) incident that did not require hospitalization.

This study concluded that the low-carbohydrate diet is a more effective strategy for long-term management of type 2 diabetes.

Individuals with uncontrolled diabetes at baseline (HbA1c levels of 11.0% or higher) were excluded from this study. Further studies are needed to confirm if these results can be applied to these patients.

If you have type 2 diabetes, talk to your doctor about the potential benefits of a low-carbohydrate diet before making any changes to how you eat.