The authors reflect a diverse group of individuals selected from physicians, scientists, nutritionists, and patient advocates with a background and experience in both metabolic health and type 1 diabetes. The final panel included 15 individuals, which is in line with recommendations for this approach.¹⁰ All authors gave consent for their participation, which was entirely voluntary.

Each author had direct contact with the main researcher (TK) to maintain communication about the study process and facilitate good response rates. Focus groups and rounds were conducted between July 2023 and July 2024 to collate research and clinical information until agreement was reached.

The authors were split up into 4 focus groups, with representation from the SMHP board (TK) attending each focus group. The resultant draft document was circulated in several rounds with each focus group for proofing and editing, culminating in a formal agreement on the final draft.

To conclude, an online anonymous survey was compiled where 17 key points were taken from the final draft and submitted for a position comment (agree or disagree), with an option to give feedback for review. Consensus was reached using predefined criteria, as follows:

The SMHP board approved the final version of the document.

Current standard treatment approaches have resulted in unsatisfactory real-world clinical results with elevated haemoglobin A1C and unacceptable rates of complications. A 2018 study revealed concerning trends: women diagnosed with T1DM before age 10 faced a lifespan nearly 18 years shorter than their counterparts without diabetes, while men in similar situations lost almost 14 years of life.¹² Moreover, cardiovascular disease, already the leading cause of death in patients without T1DM, is more prevalent among those with T1DM. Recent data from Sweden indicate a significantly elevated risk of cardiovascular mortality in patients with T1DM, with up to a tenfold increase according to glycaemic control status and age.¹³ Taken together, these real-world results suggest that the current standards are resulting in suboptimal diabetes control with regards to mortality, macrovascular complications, cardiovascular, and mental health outcomes.¹⁴

Critical to the well-being of individuals with T1DM is the integration of individualised, diabetes-focused medical nutritional therapy alongside an insulin dosing regimen.¹⁵ Although the ADA guidelines recommend reducing total carbohydrate and sugar intake using a variety of eating patterns, all dietary patterns presented, with the exception of a low-carbohydrate approach, still include starches, legumes, and grains. The inclusion of these dietary paradigms by the ADA implies counting carbohydrates and insulin bolusing is optimal when there are no randomised interventional trials showing this is the optimal approach.¹⁵

A 2014 study demonstrated that despite two years of instruction in carbohydrate counting, haemoglobin A1C levels remained high at 7.9%.¹⁶ A 2014 meta-analysis found that standard carbohydrate counting led to only a marginal haemoglobin A1C reduction of 0.3%, equating to an average blood glucose improvement of 10 mg/dL (0.6 mmol/L).¹⁷ For context, the difference between normal blood glucose levels and the average blood glucose level attained by a child with T1DM using carbohydrate counting is approximately 100 mg/dL (5.5 mmol/L). A large diabetes registry of 12,035 adults with T1DM demonstrated only 23% of subjects had a haemoglobin A1C < 7%, while 44.5% had a haemoglobin A1C of 7–9%, and 32.5% had a haemoglobin A1C > 9%.¹⁸ International comparisons, such as the 2021 Australian National Diabetes Audit, indicate a median haemoglobin A1C of 8.2% for people with T1DM, well above a healthy target (< 5.7%) and the Australian target for those with diabetes of ≤ 7.0%.¹⁹ Some of the challenges of using a high-carbohydrate diet could be explained by the difficulty of managing blood sugar levels in the setting of rapidly and slowly absorbed carbohydrate intake.

The data in Figure 1 reflect random blood glucose levels in the healthy range and are prospectively associated with an increased risk of retinopathy, peripheral neuropathy, diabetic nephropathy, peripheral arterial disease, and myocardial infarction. These data illustrate the probability of diabetes complications increasing at non-normal haemoglobin A1C levels in the mid-5% range.²⁰ Additionally, these data demonstrated that the odds of myocardial infarction increased with increased glycaemia. Recent data suggests that both glycaemia and glycaemic variability are associated with an increase in mortality in critical illness and associated with an increase in cardiovascular mortality in the chronic conditions of obesity and prediabetes.^21,22

Emerging evidence indicates that TCR may offer a promising opportunity for enhancing glycaemic control. Studies in people with type 2 diabetes have shown a direct correlation between carbohydrate intake and glycaemia,²³ suggesting that reducing carbohydrates is crucial for achieving better glycaemic outcomes in this population. The interplay between carbohydrate intake, glycaemia, and the onset of diabetes complications underscores the potential significance of TCR as a therapeutic option in T1DM.

Another somewhat under-recognised but vitally important complication of high glycaemic eating and the resulting higher insulin doses is a condition called ‘double diabetes’. This is a condition where insulin resistance and its sequelae of obesity and cardiometabolic complications occur. The prevalence is now around 25% in patients with T1DM,²⁴ and is trending upward.²⁵

The SMHP advocates for open access and clinical support for TCR for individuals with T1DM of all ages. A description of TCR will be provided, followed by an overview of the evidence and data available to demonstrate how TCR has therapeutic potential as an effective clinical intervention in T1DM.

TCR eating patterns are gaining popularity with individuals with T1D, particularly as the ADA has advised that a variety of eating patterns are acceptable for the management of diabetes and that ‘evidence suggests that there is not an ideal percentage of calories from carbohydrate, protein, and fat for people with diabetes. Therefore, macronutrient distribution should be based on an individualised assessment of current eating patterns, preferences, and metabolic goals.’¹⁵

TCR encompasses dietary interventions measured in absolute amounts (grams/day) that fall below 130 grams of dietary carbohydrate per day for specific conditions where TCR has been shown to offer therapeutic benefits.²⁶

In the research literature, TCR is often described as follows:

Other protocols of TCR have also been described for T1DM, including TCR regimens with less than 30g of total carbohydrates per day.⁹

As a way of eating that can comprise whole, nutrient-dense foods, TCR eating patterns can align with the ADA’s nutrition therapy consensus recommendations that eating patterns should:

TCR can be tailored to an individual’s preferences, values, and health goals. Various ways of eating may fall under the umbrella of TCR, including Mediterranean, Atkins, Palaeolithic, vegetarian, vegan, and carnivore dietary approaches. A variety of foods can be selected for TCR meals and snacks, including: meat, fish, eggs, leafy greens, above-ground vegetables, some fruits, and healthy fats such as olive oil, avocado, dairy products, and butter. The use of a continuous glucose monitor, or manual monitoring, can be useful in providing feedback on food choices and glycaemic variability and is recommended to help guide the process.²⁷

Note that this dietary approach for T1DM does not replicate the 4:1 or 3:1 classic ketogenic diets, which are often used therapeutically for individuals with epilepsy.²⁸ TCR nutrition therapies for T1DM prioritise dietary protein and include adequate healthy dietary fats for energy. Adequate amounts of dietary protein help meet growth, repair, and development as well as vitamin and mineral requirements. Dietary fat is used to meet energy as well as essential fatty acid and micronutrient needs. Prandial insulin dosing for TCR meals considers all macronutrients, and using exogenous insulin to cover protein in meals is particularly important when using TCR for T1DM.

For T1DM, TCR has therapeutic potential as an effective clinical intervention.

The ADA’s consensus recommendations on eating patterns address the importance of reducing overall carbohydrate intake among individuals with diabetes; highlighting this dietary approach demonstrates ‘the most evidence for improving glycaemia’.¹⁵ While directed towards type 2 diabetes and prediabetes, evidence suggests that reducing overall carbohydrate intake can also positively impact individuals with T1DM in managing glycaemia.²⁹ An analysis conducted by Lennerz et al (2021) reviewed 24 studies with varying degrees of TCR, which revealed that the degree of carbohydrate reduction associates with haemoglobin A1C in T1DM suggesting that VLCD may have the greatest impact on glycaemia (see Table 1).³⁰

Emerging data suggest that adopting TCR eating patterns can lead to improved and even optimal glycaemic control in T1DM. One study in particular demonstrated ‘exceptional glycaemic control’ and yielded promising results.³¹ In this observational study, over 300 subjects with T1DM voluntarily adhered to a VLCD, resulting in exceptional glycaemic control and low adverse event rates.³¹ Their mean haemoglobin A1c was 5.67%, with a mean daily insulin dose of 0.4 U/kg, and an average diet duration of 2.2 years ± 3.9 years. These findings underscore the effectiveness of a very low-carbohydrate (VLC) TCR eating pattern not only for improving glycaemia but also for achieving normoglycaemia in T1DM management, warranting further exploration and consideration among clinicians and patients. Despite the voluntary nature of the participants’ decision to follow a VLC TCR approach, suggesting they may have been highly motivated individuals who self-selected this therapy, the study reveals the possibility of attaining normoglycaemia in T1DM through TCR. Clinicians are encouraged to acknowledge and offer support to individuals and families who choose TCR as part of their diabetes management.

On the ketogenic end of the low-carbohydrate spectrum (<50g of carbohydrate per day), improved glycaemic control and vascular function may be experienced via a lower HbA1c, time-in-range, and reduced insulin dosing.³² A recent case study examined the cardiovascular physiology of an individual with type 1 diabetes who has followed a ketogenic diet for 10 years.³³ This individual achieved an HbA1c of 5.5% and 90% time-in-range (3.89–9.99 mmol/L) with low insulin requirements. Compared to normal findings in type 1 diabetes, health markers were favourable and included a decreased heart rate and reduced arterial stiffness, increased heart rate variability and improved endothelial function, and no sign of left ventricular diastolic dysfunction. The overall findings in this case study reflect a reduced risk of CVD relative to normal findings in individuals with type 1 diabetes.³³ In a follow-on report,³⁴ the long-term efficacy and safety of the ketogenic diet were examined. In addition to excellent glycaemic control and a 43% reduction in insulin requirements, no adverse effects were recorded on thyroid metrics, renal function, or bone mineral density. The overall lipid profile did not appear to increase the risk of CVD.^33,34 While this is a single case report, the findings are encouraging and invite further study.

While VLC diets show significant promise for T1DM management, there are also benefits observed from reducing carbohydrate intake from traditional high-carbohydrate diets. A randomised, crossover trial conducted by Sterner Isaksson et al. (2023) compared interventions with 30% of energy from carbohydrate (moderate carbohydrate) versus 50% of energy from carbohydrate (traditional diet) followed by individuals with T1DM with baseline haemoglobin A1C levels of ≥ 7.5% (≥ 58 mmol/mol).²⁹ The study revealed that reducing carbohydrate intake led to significantly lower mean glucose levels (a mean difference of -0.6 mmol/L). Additionally, participants experienced more time in range and tighter range (though the majority did not reach the target of 70% time in range), less time with high and very high glucose levels, and increased treatment satisfaction. This highlights the potential of even modest reductions in dietary carbohydrate, suggesting a step in the right direction for improving glycaemic control and diabetes outcomes, even though studies indicate that VLC and low-carbohydrate eating patterns yield better results.

Given the significant concern surrounding hypoglycaemia in individuals with T1DM and their healthcare providers, TCR presents a potential approach for reducing the risk of hypoglycaemia. While hypoglycaemia is mainly a result of excessive or poorly-timed administration of exogenous insulin, the choice of food can influence the amount of insulin needed for a meal. Opting for an eating pattern that requires less insulin coverage may lower the risk of hypoglycaemic episodes, though further studies are required to systematically demonstrate this.

While a recent clinical trial by Turton et al. (2023) found no significant difference in the frequency of hypoglycaemic episodes between TCR and a diet consisting of over 150g of carbohydrates daily, various clinical case studies and trials, including those conducted by Nielsen (2005, 2012), Schmidt (2019), Ranjan (2017), and Mahmood (2023), have reported substantial improvements in the rate of hypoglycaemia or a reduction in the duration spent in hypoglycaemia.^{35,36,37,38,39,40} A clinical report by Nielsen (2005) revealed that individuals adhering to TCR experienced a reduction in the mean rate of symptomatic hypoglycaemia by 94% after three months and 82% at twelve months from baseline.³⁶ Additional studies examining TCR’s impact on hypoglycaemia are warranted.

The current evidence does not suggest an increased risk of diabetic ketoacidosis (DKA) in individuals with T1DM who adhere to a TCR eating pattern. With sufficient insulin and effective blood glucose management, individuals with T1DM can safely follow TCR. Findings from research trials and clinical case studies have suggested no incidence of or elevated risk of DKA compared with prevailing rates.^{29,31,35,38,39,41} However, it’s important to note that all individuals with T1DM, regardless of dietary patterns, are susceptible to DKA and more systematic studies are needed. All individuals with T1DM should have a sick day management plan in place for times when they may be more vulnerable to DKA.

Patients with T1DM often experience comorbidities such as obesity,⁴² metabolic syndrome,⁴³ hypertension, and insulin resistance.² The prevalence of obesity among people with T1DM, historically typically lean, has reached epidemic levels, contributing to the emerging phenomenon of ‘double diabetes’,^44,45,46 which occurs when an individual with T1DM develops insulin resistance characteristics of metabolic syndrome and type 2 diabetes.⁴⁷

This sub-type of diabetes, where insulin resistance has occurred, is more at risk of micro- and macrovascular disease.^1,2 Studies reflect a higher incidence of complications in this sub-group, irrespective of glycaemic control, indicating that poor glycaemic control is not the sole driver of complications in type 1 diabetes. Insulin requirement or insulin resistance is an important and independent risk factor even in well controlled type 1 diabetes.² Restoring or maintaining insulin sensitivity could be a significant step towards improving outcomes in type 1 diabetes, particularly given some inconsistencies in outcomes relating to glycaemic control alone.⁴⁸ Reduced insulin dosing is a feature of therapeutic carbohydrate reduction in the management of type 1 diabetes and therefore represents a strategy that may mitigate the development of double diabetes.^32,34

Patients with T1DM experience comorbid major depression and depressive symptoms at a rate of 11% and 31%, respectively.⁴⁹ Psychological issues and, separately, diminished quality of life have both been linked with suboptimal glycaemic control and diabetes complications. In light of these comorbidities and early evidence,⁵ TCR should be more widely studied.

Low-carbohydrate diets have been extensively studied for obesity and have consistently shown superior results for weight loss, even in systemic analysis.⁵⁰ Calorie-controlled studies have also demonstrated that therapeutic carbohydrate reduction preferentially improves markers of metabolic syndrome.⁵¹ VLCD have been compared head-to-head with the DASH diet and the Mediterranean diet in clinical settings. Against the DASH diet, low-carbohydrate diets were found to be superior for reducing blood pressure, weight, and glycaemia.⁵² When directly compared to the Mediterranean diet, the ketogenic diet was found to decrease the need for diabetes medications in a sensitivity analysis, demonstrating improved glycaemia in patients with prediabetes and type 2 diabetes.⁵³

Double diabetes has been used to refer to individuals with T1DM who are overweight, have a family history of type 2 diabetes and/or have clinical features of insulin resistance.⁵⁴ It has been suggested that TCR may help protect individuals with T1DM from excessive weight gain, inflammation, and atherosclerosis and from developing metabolic syndrome, Alzheimer’s disease, and cancer by addressing insulin resistance.⁵⁵

While further robust research, including comparative trials, on TCR for T1DM is warranted, the available evidence indicates TCR’s safety and potential efficacy as a dietary intervention. The SMHP encourages clinicians to acknowledge and offer support to individuals and families who choose TCR as part of their diabetes management, fostering an environment that embraces a variety of eating patterns for the management of diabetes and respects patient autonomy.

MNT is quite confusing where most approaches still recommend starches, grains, legumes, and high-sugar fruit, which is antithetical to their recommendations to reduce overall carbohydrate and sugar intake. The current MNT promoted by professional diabetes associations is deemed inadequate by the SMHP, resulting in adverse outcomes. We must not settle for the status quo in T1DM management.

With emerging evidence demonstrating the efficacy of TCR nutritional therapy for people with T1DM, it is crucial to initiate systematic changes to incorporate TCR approaches. To address this, the SMHP recommends the following systematic changes: