The study included 316 individuals, of whom 54% were adult patients and 42% were parents of children with type 1 diabetes. All were part of an international Facebook group for people with type 1 diabetes who follow Bernstein's recommended VLCD diet.
The approach includes a weight-based carbohydrate prescription of no more than 30 grams/day, derived from fibrous vegetables and nuts with a low glycemic index. High-protein foods are substituted for carbohydrates, and insulin doses adjusted empirically by postprandial and fasting glucose levels.
Most of the participants were from the United States, Canada, Europe, or Australia, the majority (88%) were white, and 84% were college graduates. Mean age at diabetes diagnosis was 16 years, diabetes duration was 11 years, and time following the VLCD diet was 2.2 years.
Confirmatory data were obtained from diabetes care providers and medical records, including a multi-tiered investigation to ensure all participants had type 1 diabetes — not type 2 diabetes or a genetic variant. However, not all data points were available for all respondents.
Participants reported consuming an average of 36 grams/day of carbohydrate. The mean reported HbA1c was 5.67%, a drop of 1.45 percentage points following adoption of the VLCD (P < .001). Average blood glucose level was 104 mg/dL in the 137 patients who had continuous glucose monitoring data.
In a regression analysis, carbohydrate intake goal was the only significant predictor of variation in HbA1c (P = .001), with an increase in HbA1c of 0.1% per 10 g of carbohydrate consumed. The mean daily insulin dose was 0.40 U/kg/day.