Does a low-carbohydrate diet improve outcomes more than a moderate-carbohydrate diet in patients with prediabetes or Type 2 diabetes?

This study investigated the outcomes of a very low-carbohydrate (ketogenic) diet versus a moderate-carbohydrate diet in adults with prediabetes or Type 2 diabetes. This study concluded that the adults on the low-carbohydrate diet had greater reductions in HbA1c levels (average blood glucose over 3 months), body weight, and medication usage compared to those on the moderate-carbohydrate diet.

Dietary management is an important component of the treatment of type 2 diabetes mellitus (T2D) However, the optimal diet for managing T2D remains unclear. Previous research has suggested that a very low-carbohydrate (ketogenic) diet may improve metabolic outcomes and reduce usage of diabetes-related medication. Whether this type of diet leads to better outcomes than diets with higher carbohydrate intake remains under investigation.

This study involved 34 overweight adults with prediabetes or T2D. 47% were placed on a very low-carbohydrate diet (LCD) and 53% were placed on a moderate-carbohydrate diet (MCD) for 12 months. 47% of all participants reported taking diabetes-related medication. Of these, 29.4% were in the LCD group and 17.6% were in the MCD group. All participants also received lifestyle recommendations (physical activity and sleep). Outcomes were determined at 6 months and at 12 months.

At 12 months, participants in the LCD group had a 0.5% reduction in HbA1c levels (from 6.6% to 6.1%) compared to a 0.2% reduction (from 6.9% to 6.7%) in the MCD group. At 6 months, HbA1c levels were 6.0 (LCD) and 6.7 (MCD).

At 12 months, the LCD group lost 7.9 kg in body weight (from 99.9 to 92.0 kg) compared to the MCD group (1.7 kg lost, from 97.5 to 95.8 kg). BMI also decreased more in the LCD group (decrease of 2.6) compared to the MCD group (decrease of 0.9). At 6 months, body weight was 93.8 kg (LCD) and 95.8 kg (MCD). These differences were statistically significant.

At 12 months, the LCD group had higher cholesterol (increase of 6.9) than the MCD group (increase of 2.0). At 6 months, LDL cholesterol levels increased by 9.2 (LCD) and decreased by 10 (MCD). Only the levels at 6 months were significantly different between the two groups.

At 12 months, 60% (LCD) and 0% (MCD) of participants taking diabetic medications at the beginning of the study stopped taking them. 11.1% of the MCD group started medication, compared to 0% in the LCD group. These differences were statistically significant.

This study concluded that the adults on the low-carbohydrate diet had greater reductions in HbA1c levels, body weight, and medication usage compared to those on the moderate-carbohydrate diet.

The sample size of this study is quite small, which limits the conclusions that may be drawn from these results. Also, because both groups received lifestyle recommendations, it is possible that these changes also impacted the outcomes. Larger studies investigating outcomes beyond 12 months are needed to further support these results.

If you are overweight and have prediabetes or non-insulin dependent Type 2 diabetes, talk to your doctor about the potential benefits of following a very low-carbohydrate diet. It is important to always discuss dietary changes with your doctore before putting them into practice.