Introduction

An observational study published in 2024 that followed over 2,000 adults with type 1 diabetes (T1D) from the T1D Exchange Registry showed that despite advanced technologies like continuous glucose monitors (CGM) and automated insulin delivery (AID), over 40% of participants were not meeting the HbA1c (glycated haemoglobin) targets set by the American Diabetes Association [1, 2].  

The high percentage of individuals struggling to meet HbA1c targets with current treatments suggests the need for alternative intervention strategies to improve blood glucose control in people living with T1D. Encouragingly, research indicates that dietary modifications, such as reducing carbohydrate intake, could offer a promising solution. These dietary changes may be effective for weight management and preventing episodes of hypo- and hyperglycaemia [3].

But how strong are the arguments in favour of low-carbohydrate diets (LCDs), and how solid is the research backing them? If you're considering switching to an LCD, is it safe and feasible?

In this chapter, we’ll examine the known pros and cons of LCDs for people with T1D. We aim to provide a neutral overview of the literature and empower you, whether you’re living with diabetes or are a healthcare provider, to make better-informed, evidence-based decisions about the suitability of LCDs while being mindful of the potential risks and limitations.

 

A Brief History of Carbohydrate Restriction and T1D

Before delving into the potential pros and cons of LCDs, let's quickly explore the history of nutritional guidelines and how they have evolved, particularly in relation to carbohydrate restriction in T1D.

The history of carbohydrate restriction in T1D is rooted more in necessity than choice. Before the discovery of insulin in 1921, treatment options for T1D were extremely limited and largely ineffective. One common method was the "starvation diet" or "diabetic diet," developed in the late 19th and early 20th centuries [4]. This diet involved severely restricting intake to around 450-600 calories per day, focusing on low-carbohydrate, high-fat, and high-protein foods (Figure 1). The goal was to reduce the amount of sugar in the urine, which was believed to be the cause of diabetes. Patients on this diet would often experience rapid weight loss, malnutrition, and other serious health problems [5].