Abstract
Background and Objectives: Carbohydrate-restricted diets have recently become popular among patients with type 1 and type 2 diabetes mellitus. Research has shown that a carbohydrate-restricted diet may benefit glycaemic control and assist weight loss for people with type 1 diabetes. For those following a carbohydrate-restricted diet, an insulin-to-carbohydrate ratio may be inadequate. An additional insulin bolus for meal protein content may help reduce post-prandial glycaemia. This study aimed to evaluate the use of an insulin-to-protein ratio in addition to an insulin-to-carbohydrate ratio over 12 weeks in people with type 1 diabetes who habitually follow a carbohydrate-restricted diet.
Methods and Study Design: Participants (n=34) with type 1 diabetes aged 18-years and over who were using a basal-bolus insulin regimen were randomly allocated (1:1) to either carbohydrate and protein-based insulin dosing or carbohydrate-based insulin dosing alone. All participants followed a carbohydrate-restricted diet (50-100g per day). Participants attended a total of four or five visits at the Centre of Endocrine, Diabetes and Obesity Research. All participants attended an initial screening visit and those who consumed >100g carbohydrate per day attended an additional visit before randomisation in order to transition to the carbohydrate-restricted diet. Participants attended visits at baseline and 12 weeks for measurement of haemoglobin A1c, weight, height and blood pressure. Two-week food diaries and continuous glucose monitors were given to participants two weeks prior to each of these visits. Participants
filled in a questionnaire about their experience of the insulin regimen at the last visit.
Results: A total of 34 participants were recruited of which 16 were randomly assigned to the intervention group and 18 to the control group. There was one withdrawal from the intervention group and two withdrawals from the control group. The intervention group did not have any significant improvements in haemoglobin A1c, glycaemic variability, time spent in normal glycaemic range or hyperglycaemia compared with the control group. However, there was no significant increase in time spent in hypoglycaemia for either group. There were no significant changes in weight or BP for either group. Qualitative data indicated that some participants found the insulin-to-protein ratio helped them feel more in control of their diabetes while others found that it increased their distress.
Conclusion: An insulin-to-protein ratio in addition to an insulin-to-carbohydrate ratio did not improve glycaemic control in patients with type 1 diabetes who follow a carbohydrate-restricted diet. However, the risk of hypoglycaemia did not increase. The findings of this study support individualisation of management. Patients may choose to use an insulin-to-protein ratio if they find it helps them feel more in control of their diabetes. However, it should not be used if it increases distress.