Research Update: Therapeutic Carbohydrate Restriction for Metabolic Syndrome and Type 2 Diabetes

Sarah Rice BSc. (Hons), MCOptom (UK), MHP, NNP

Introduction

The rise of metabolic syndrome and type 2 diabetes continues unabated, with no sign of improvement. This is a public health crisis, as the number of individuals affected by metabolic syndrome globally is reported at 20%–45%, with projections for over 50 % by 2035 (1) Likewise, those with type 2 diabetes, an associated condition, have risen from 200 million in 1990 to 830 million in 2022, carrying with it a crushing economic burden (2). Even with the ongoing development of new diabetes medications, only approximately 50% of patients achieve optimal glycaemic goals. Specifics vary between countries but approximate goals are glycated haemoglobin (HbA1c) < 7% or time in range (% time with glucose 70-180 mg/dL [3.9–10 mmol/L]) > 70% (3).

Despite a long history of therapeutic use, TCR for metabolic syndrome and type 2 diabetes in the modern era has taken a while to be accepted. Pioneers in the TCR space have worked tirelessly to expand the evidence base and present TCR as a safe and effective intervention. Recently, a number of systematic reviews have looked at the data for TCR in populations with metabolic syndrome, type 2 diabetes, and CGM use compared to a standard glucometer. 

International agencies are now recognising the validity of a reduced carbohydrate approach, with the American Diabetes Association stating in its Standards of Care in Diabetes—2025, ‘low-carbohydrate and very-low-carbohydrate eating patterns have been found to reduce A1C and the need for glucose-lowering medication’ (4).

These studies and acknowledgements serve as a timely reminder that TCR should be considered as one of the first-line options for people with metabolic syndrome or type 2 diabetes.

Metabolic health

Feng et al. (2025) conducted a comprehensive meta-analysis incorporating 149 randomised controlled trials involving over 9,104 adults to systematically evaluate the effects of various Carbohydrate-Restricted Diets (CRDs) on a broad panel of metabolic health biomarkers (1). The overall results demonstrated that CRDs conferred significant metabolic benefits compared to higher-carbohydrate diets, notably improving glycaemic control (reducing glucose, HbA1c, insulin, and HOMA-IR), hepatic stress, and renal function. Subgroup analyses revealed that LCDs (10–26% energy from carbs) and MCDs (26–45% energy from carbs) showed consistent metabolic improvements, with ketogenic diets producing the greatest reductions in blood glucose and insulin concentrations (some increase in one liver enzyme reported). Macronutrient ratios and fat subtypes influenced metrics, which improved irrespective of energy intake. The benefits increased in subgroups characterised by metabolic dysfunction, including individuals with T2DM, females, and those classified as overweight or obese.

Type 2 diabetes

This systematic review by Das et al. (2025) evaluated the long-term efficacy and safety of low-carbohydrate diets (LCDs) and ketogenic diets (KDs) (carbohydrate range: <130 g/day to <50 g/day) in the management and remission of T2DM, synthesising data from six clinical trials with follow-up durations ranging from one to eight years (2). The review confirms that LCDs and KDs are effective strategies, leading to significant reductions in key metabolic markers, including HbA1c, body weight, BMI, and systolic blood pressure.

T2DM remission, defined as HbA1c <6.5% without glucose-lowering medications for at least three months, was achieved in a significant proportion of participants; remission rates peaked at 1 year (up to ~62%) then declined (~13% at 5 years), with remission strongly associated with the degree of weight loss ( ≥10–15 kg). The dietary interventions were also associated with substantial reductions in dependency on both glucose-lowering and antihypertensive medications. Dietary interventions were safe and effective, with no significant adverse events reported in long-term trials. Personalised dietary approaches and appropriate support are key to long-term success.

Continuous Glucose Monitoring

Willis et al. (2025) conducted a 6-month randomised clinical trial in adults with T2D who were undergoing a carbohydrate-restricted nutrition programme, comparing the outcomes between continuous glucose monitoring (CGM) and conventional self-monitoring of blood glucose (SMBG) (3). Both arms experienced clinically meaningful HbA1c (mean 6-month values of 6.5% [CGM] and 6.8% [BGM]) and weight reductions (approximately 10–11 kg total loss). The CGM arm demonstrated faster improvements in time-in-range and greater early reductions in HbA1c, with higher measured adherence to carbohydrate targets and fewer hypoglycaemic episodes requiring intervention. Participants using CGM had earlier, more frequent medication reductions and reported higher self-efficacy scores. The study concluded that the large glycaemic impact of the ketogenic diet, coupled with continuous remote care, likely outweighed any potential differential benefit of the glucose monitoring method.

Insulin resistance and hyperinsulinaemia

A recent paper from Fazio et al. (2025) examines the relationship between insulin resistance and hyperinsulinaemia and long-term health problems, finding associations with increased mortality (cardiovascular, cancer-related, and all-cause mortality) and also with cellular ageing, cancer, and neurodegenerative disorders (5). They conclude with a call to action, recommending that insulin resistance and hyperinsulinemia be recognised as independent risk factors and screened in the general population to enable early intervention.

Conclusion

Overall, these studies highlight the role of insulin resistance and hyperinsulinaemia in chronic disease and confirm that carbohydrate restriction is a highly effective strategy for improving glycaemia, reducing medication burden, and promoting weight loss in individuals with metabolic syndrome and type 2 diabetes. Long-term adherence remains a limiting factor, and researching optimal implementation and support strategies could provide insights that increase success for a greater proportion of those choosing this approach.

Resources

Nutrition Network offers a range of training programmes that equip practitioners to support their patients’ or clients’ successful adoption of TCR for metabolic disorders. These include trainings that address processed food addiction, different patient populations, and group coaching structures. Patient training options are also available.

References

1. Feng, S., Liu, R., Colwell, B., et al. (2025) ‘Carbohydrate-restricted diet types and macronutrient replacements for metabolic health in adults: A meta-analysis of randomized trials’, Clinical Nutrition, p. S0261561425002535. Available at: https://doi.org/10.1016/j.clnu.2025.09.005. 
2. Das, R. et al. (2025) ‘Long-Term Efficacy and Safety of a Low-Carbohydrate Diet in Type 2 Diabetes Remission: A Systematic Review’, Cureus, 17(9), p. e93340. Available at: https://doi.org/10.7759/cureus.93340. 
3. Willis, H.J. et al. (2025) ‘Effects of Continuous Glucose Monitoring Versus Blood Glucose Monitoring During a Carbohydrate-Restricted Nutrition Intervention in People With Type 2 Diabetes: 6-Month Follow-up Outcomes From a Randomized Clinical Trial’, Endocrine Practice, 31(9), pp. 1116–1126. Available at: https://doi.org/10.1016/j.eprac.2025.05.746.
4. American Diabetes Association Professional Practice Committee (2024) ‘5. Facilitating Positive Health Behaviors and Well-being to Improve Health Outcomes: Standards of Care in Diabetes—2025’, Diabetes Care, 48(Supplement_1), pp. S86–S127. Available at: https://doi.org/10.2337/dc25-S005.
5. Fazio, S., Fazio, V., & Affuso, F. (2025). The link between insulin resistance, hyperinsulinemia and increased mortality risk. Academia Medicine.  https://doi.org/10.20935/AcadMed7786.