1. In this randomized controlled trial, sustained low-carbohydrate diet in patients with untreated hemoglobin A1c of 6.0%-6.9% led to improved hemoglobin A1c and glycemic control.

2. Furthermore, sustained low-carbohydrate diet in this patient sample led to decreased caloric intake and significant weight loss.

Evidence Rating Level: 2 (Good)

Type 2 diabetes (T2D) is rapidly increasing in prevalence and has a high disease burden in the United States (US). Diet plays a crucial role in managing T2D, and in patients with T2D, low carbohydrate diets have been shown to be associated with a reduction in hemoglobin A1c (HbA1c) in a linear fashion. However, whether a low-carbohydrate diet could have beneficial effects in patients with untreated diabetes or prediabetes has not been extensively studied. 

This study was a randomized control trial that included 150 participants from Louisiana, US, aged 40 to 70 years old, with an HbA1c in the range of 6.0-6.9%. Participants with type-1 diabetes or currently on glucose-lowering medications were excluded. 75 participants were randomized to low-carbohydrate diet intervention (<40 net grams of carbohydrate for months 0-3 and <60g of carbohydrate for months 3-6) and 75 participants to usual diet. The intervention low-carbohydrate group also received weekly nutritional counseling. The primary outcome was change in HbA1c measured at 0, 3, and 6 months.

Compared to the usual diet group, the low-carbohydrate group had significantly greater reduction in HbA1c (-0.23% net difference) as well as fasting plasma glucose (-10.3mg/dL net difference) and body weight (-5.9kg net difference). However, this study was limited by the potential confounder of significant weight loss and decreased overall caloric intake in the low-carbohydrate group, which could have directly led to improved glycemic control independent of the low-carbohydrate nature of the diet. However, these results suggest that low-carbohydrate diet could be considered as an option for improved glycemic control for patients at high risk of T2D, warranting further studies with prolonged follow-up and direct comparison with other diet types.

 Click to read the study in JAMA Network Open 

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