Research Highlight: Low-Carbohydrate and Ketogenic Diets in Type 1 Diabetes

Sarah M. Rice

Sarah M. Rice

Introduction

Recent research has explored the impact of low-carbohydrate and ketogenic dietary interventions in individuals with type 1 diabetes (T1D), focusing on metabolic, body composition, and cardiovascular outcomes. The two studies highlighted here add to existing data on the short-term and long-term effects of carbohydrate reduction in this population.

Short-Term Low-Carbohydrate Diets in Children and Adolescents

A randomised controlled crossover study investigated the effects of a tightly controlled low-carbohydrate diet (LCD; 95 g/day) versus a recommended carbohydrate diet (RCD; ~191 g/day) over two five-week periods in children and young people with T1D (1). There was no clinically meaningful difference in the average daily energy intake for the two periods. The primary outcomes included body weight, body mass index (BMI), body fat percentage, and muscle strength, with isocaloric intake maintained across interventions.

The LCD period resulted in statistically significant reductions in body weight (61.7 kg vs. 62.6 kg, P<0.001), BMI (22.3 kg/m² vs. 22.7 kg/m², P<0.001), and body fat percentage (24.5% vs. 25.3%, P=0.001) compared to the RCD period. Importantly, dynamic muscle function, as assessed by jumping mechanography, did not differ significantly between the two dietary interventions, indicating that short-term carbohydrate reduction did not negatively impact muscle strength in this cohort. These findings suggest that a short-term LCD can be an effective strategy for reducing adiposity in paediatric T1D without compromising muscle function (1).

Long-Term Ketogenic Diet and Cardiovascular Health in an Adult

In contrast, a case report examined the long-term cardiovascular effects of a ketogenic diet (≤50 g carbohydrate/day) in an adult male (33 years old) with T1D (2). Over a 10-year period, the individual adhered to a ketogenic diet and achieved an HbA1c of 5.5% with lowered daily insulin use (euglycaemia of <5.7% HbA1c is obtained in <1% of the T1D population). Despite having elevated low-density lipoprotein (LDL) cholesterol (129 mg/dL – in the context of diabetes this may be considered elevated) and not using lipid-lowering medication, they demonstrated zero detectable coronary artery calcification (CAC) at age 30–39. This case is notable given that 30–70% of males with T1D in this age group typically have a CAC score >1, indicating subclinical atherosclerosis. The absence of detectable CAC in this case indicates a lack of atherosclerotic plaque formation, challenging concerns about the long-term cardiovascular risks of ketogenic diets in T1D, particularly in the context of elevated LDL (2).

Clinical Implications and Considerations

These studies point to the potential benefits of carbohydrate-reduced diets in T1D for improving body composition and suggest that favourable cardiovascular health can be maintained over the longer term.

While these data have limitations, the results demand further large-scale, long-term studies to determine the safety, metabolic, and cardiovascular outcomes of carbohydrate-reduced diets in T1D populations.

Conclusion

Emerging evidence suggests that low-carbohydrate and ketogenic diets may offer metabolic and potential cardiovascular benefits for T1D, but robust, long-term clinical trials are required to inform guidelines and optimise patient care.

References

1. Neuman, V. et al. (2025) ‘Short-term low-carbohydrate diet decreases body weight and fat mass but not muscle strength in children and young people with type 1 diabetes’, European Journal of Clinical Nutrition, 79(11), pp. 1149–1153. Available at: https://doi.org/10.1038/s41430-025-01658-2.

2. Koutnik, A.P. et al. (2025) ‘Coronary Artery Calcification in Type 1 Diabetes After 10-Year Ketogenic Diet’, Journal of Applied Physiology [Preprint]. Available at: https://doi.org/10.1152/japplphysiol.00893.2025.

Additional reading

3. Koutnik, A.P. et al. (2024) ‘Efficacy and Safety of Long-term Ketogenic Diet Therapy in a Patient With Type 1 Diabetes’, JCEM Case Reports, 2(7), p. luae102. Available at: https://doi.org/10.1210/jcemcr/luae102.

4. Watso, J.C. et al. (2024) ‘Advanced Cardiovascular Physiology in an Individual with Type 1 Diabetes After 10-Year Ketogenic Diet’, American Journal of Physiology-Cell Physiology [Preprint]. Available at: https://doi.org/10.1152/ajpcell.00694.2023.

5. Kalayjian, T. et al. (2024) ‘The SMHP™ position statement on therapeutic carbohydrate reduction for type 1 diabetes’, Journal of Metabolic Health, 7(1), p. 9. Available at: https://doi.org/10.4102/jmh.v7i1.100.

6. McNally, B. et al. (2024) ‘A GUIDE FOR DIETITIANS & NUTRITIONISTS’. Available at: https://www.therapeuticnutrition.org/tcr-type-1-diabetes-guide (Accessed: 23 March 2025). [Implementation guide using TCR for type 1 diabetes]