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NNEdPro Global Institute for Food, Nutrition and Health: Position Statement on low carbohydrate diets in the management of type 2 diabetes

Authors: Dr Dominic Crocombe & Dr Rajna Golubic 

Reviewers and Editors: Ramya Rajaram, Sumantra Ray 

Copyediting: Veronica Funk 


Diet is a key factor in the development, progression, and outcomes of many chronic diseases. Since its inception, NNEdPro Global Institute for Food, Nutrition and Health (NNEdPro Global Institute) has supported the research, development, and implementation of safe, effective and sustainable dietary interventions, including for type 2 diabetes mellitus (T2D). There is particularly good clinical evidence to support energy restricted diets to induce weight loss and subsequent remission of T2D (1,2), especially for low and/or very low calorie diets following the success of the DiRECT trial in the UK (3).


In recent years, the body of evidence for low carbohydrate diets (LCDs) to achieve the same goals has also grown. NNEdPro Global Institute is proud to have contributed research on this topic and has published a number of scientific papers, including in our journal, BMJ Nutrition, Prevention and Health (4–7). In 2020, we published the clinical outcomes of an innovative NHS primary care service in which a LCD approach was offered to patients with T2D under the clinical supervision of Dr David Unwin at the Norwood Surgery (4). This initial paper reported the outcomes of 128 patients with T2D (27% of the total practice population who had T2D) who had been counselled and supported to follow a LCD over an average of 23 months. Significant improvements in body weight, glycaemic control, other cardiometabolic markers, and reduced the need for T2D medications were demonstrated. Remarkably, the rate of drug-free T2D remission, which is of utmost importance to long-term health outcomes (8), was 46%. Encouragingly, positive results were seen across a wide range of patients, including those of older age (>65 years), those with long-standing T2D (>6 years since diagnosis), and those with high baseline HbA1c.


We also observed a significant improvement in lipid profile in this cohort, which predominantly comprised overweight or obese adults. However, we are aware of the emerging evidence of differential lipid responses to LCD according to adiposity. This phenomenon is termed the “lean mass hyper-responder phenotype” whereby consumption of LCD is associated with an elevated low density lipoprotein cholesterol in those with normal body weight but not in those with elevated body weight (9). Further studies from the Norwood Surgery cohort have suggested an improvement in renal function with a LCD, despite some concerns that a LCD may be detrimental to kidney health (10), and that patients in their first year of T2D diagnosis were particularly likely to achieve remission (5).


It is worth noting that all results from the Norwood Surgery to date have come from retrospective clinical service evaluation/audit, and all patients had opted for the LCD intervention without randomisation or a formal control group. There are limitations to this research, especially in comparison to formal interventional trials, but the results are insightful, remarkable in their impact (both clinically and financially), and they make a compelling case for the potential of LCD interventions in routine clinical practice. Furthermore, the mechanisms that make clinical trials superior in the hierarchy of evidence, namely control groups, randomisation, and blinding, are notoriously difficult to implement in dietary intervention trials. We have commented further on the utility of both clinical audit and science-led research for dietary interventions elsewhere (6).


In recent years, several more studies have reported in favour of LCDs in T2D. These include population-level studies (11), clinical trials (12–14), and systematic reviews and meta-analyses of existing evidence, amongst which is evidence of a dose-response relationship between reducing carbohydrate intake and positive outcomes (15–18). Others have highlighted how the quality of carbohydrates eaten, and indeed the quality of the overall diet, are also important considerations (11,19).


Other points worth noting include a recent clinical trial of vegetarian and vegan LCDs in patients with T2D, which demonstrated effectiveness in clinical parameters, and a potentially favourable impact on greenhouse gas emissions for vegan LCDs (13). Finally, the LCD approach for T2D and other metabolic conditions has been demonstrated to be beneficial when provided via novel care models, including large scale telemedicine services (20,21). Important issues still open to debate include the definition of low (and/or very low) carbohydrate diets or ketogenic diets, the physiological effects of LCDs independent of weight loss, and the best strategies for implementation and long-term maintenance.


In summary, we at NNEdPro Global Institute celebrate the growing acceptance that T2D remission is possible through dietary modification. Low and very low-calorie diets have a robust evidence base for this indication. The evidence base for LCDs is growing and this should be considered another valid option that is offered to patients with T2D. Modern healthcare systems would be of greater benefit to patients with T2D for expanding their nutrition and dietetics workforces. This, in addition to better nutrition education and training for all healthcare professionals providing care to patients with T2D is strongly recommended.  



References

1. Taylor R, Ramachandran A, Yancy WS, Forouhi NG. Nutritional basis of type 2 diabetes remission. BMJ. 2021 Jul 7;374:n1449.

2. Churuangsuk C, Hall J, Reynolds A, Griffin SJ, Combet E, Lean MEJ. Diets for weight management in adults with type 2 diabetes: an umbrella review of published meta-analyses and systematic review of trials of diets for diabetes remission. Diabetologia. 2022 Jan 1;65(1):14–36.

3. Lean ME, Leslie WS, Barnes AC, Brosnahan N, Thom G, McCombie L, et al. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. The Lancet. 2018 Feb 10;391(10120):541–51.

4. Unwin D, Khalid AA, Unwin J, Crocombe D, Delon C, Martyn K, et al. Insights from a general practice service evaluation supporting a lower carbohydrate diet in patients with type 2 diabetes mellitus and prediabetes: a secondary analysis of routine clinic data including HbA1c, weight and prescribing over 6 years. BMJ Nutrition, Prevention & Health [Internet]. 2020 Dec 1 [cited 2024 Jan 20];3(2). Available from: https://nutrition.bmj.com/content/3/2/285

5. Unwin D, Delon C, Unwin J, Tobin S, Taylor R. What predicts drug-free type 2 diabetes remission? Insights from an 8-year general practice service evaluation of a lower carbohydrate diet with weight loss. BMJ Nutrition, Prevention & Health [Internet]. 2023 Jun 1 [cited 2024 Jan 20];6(1). Available from: https://nutrition.bmj.com/content/6/1/46

6. McAuliffe S, Unwin D, Bradfield J, Ray S, Martyn K. Bridging the gap between science-led research and evaluation of clinical practice: the role of service innovation audits and case studies. BMJ Nutrition, Prevention & Health [Internet]. 2021 Jun 1 [cited 2024 Jan 20];4(1). Available from: https://nutrition.bmj.com/content/4/1/350

7. Cupit C, Redman E. Supporting people to implement a reduced carbohydrate diet: a qualitative study in family practice. BMJ Nutrition, Prevention & Health [Internet]. 2021 Jun 1 [cited 2024 Jan 20];4(1). Available from: https://nutrition.bmj.com/content/4/1/226

8. Gregg EW, Chen H, Bancks MP, Manalac R, Maruthur N, Munshi M, et al. Impact of remission from type 2 diabetes on long-term health outcomes: findings from the Look AHEAD study. Diabetologia [Internet]. 2024 Jan 18 [cited 2024 Jan 20]; Available from: https://doi.org/10.1007/s00125-023-06048-6

9.  Soto-Mota A, Flores-Jurado Y, Norwitz NG, Feldman D, Pereira MA, Danaei G, et al. Increased LDL-cholesterol on a low-carbohydrate diet in adults with normal but not high body weight: a meta-analysis. The American Journal of Clinical Nutrition. 2024 Jan;S0002916524000091.

10. Unwin D, Unwin J, Crocombe D, Delon C, Guess N, Wong C. Renal function in patients following a low carbohydrate diet for type 2 diabetes: a review of the literature and analysis of routine clinical data from a primary care service over 7 years. Current Opinion in Endocrinology, Diabetes and Obesity. 2021 Oct;28(5):469.

11. Hu Y, Liu G, Yu E, Wang B, Wittenbecher C, Manson JE, et al. Low-Carbohydrate Diet Scores and Mortality Among Adults With Incident Type 2 Diabetes. Diabetes Care. 2023 Feb 14;46(4):874–84.

12. Gram-Kampmann EM, Hansen CD, Hugger MB, Jensen JM, Brønd JC, Hermann AP, et al. Effects of a 6-month, low-carbohydrate diet on glycaemic control, body composition, and cardiovascular risk factors in patients with type 2 diabetes: An open-label randomized controlled trial. Diabetes, Obesity and Metabolism. 2022;24(4):693–703.

13. Jenkins DJ, Jones PJ, Abdullah MM, Lamarche B, Faulkner D, Patel D, et al. Low-carbohydrate vegan diets in diabetes for weight loss and sustainability: a randomized controlled trial. The American Journal of Clinical Nutrition. 2022 Nov 1;116(5):1240–50.

14. Durrer C, McKelvey S, Singer J, Batterham AM, Johnson JD, Gudmundson K, et al. A randomized controlled trial of pharmacist-led therapeutic carbohydrate and energy restriction in type 2 diabetes. Nat Commun. 2021 Sep 10;12(1):5367.

15. Soltani S, Jayedi A, Abdollahi S, Vasmehjani AA, Meshkini F, Shab-Bidar S. Effect of carbohydrate restriction on body weight in overweight and obese adults: a systematic review and dose–response meta-analysis of 110 randomized controlled trials. Frontiers in Nutrition [Internet]. 2023 [cited 2024 Jan 20];10. Available from: https://www.frontiersin.org/articles/10.3389/fnut.2023.1287987

16.         Nicholas AP, Soto-Mota A, Lambert H, Collins AL. Restricting carbohydrates and calories in the treatment of type 2 diabetes: a systematic review of the effectiveness of ‘low-carbohydrate’ interventions with differing energy levels. Journal of Nutritional Science. 2021 Jan;10:e76.

17. Goldenberg JZ, Day A, Brinkworth GD, Sato J, Yamada S, Jönsson T, et al. Efficacy and safety of low and very low carbohydrate diets for type 2 diabetes remission: systematic review and meta-analysis of published and unpublished randomized trial data. BMJ. 2021 Jan 13;372:m4743.

18. Jayedi A, Zeraattalab-Motlagh S, Jabbarzadeh B, Hosseini Y, Jibril AT, Shahinfar H, et al. Dose-dependent effect of carbohydrate restriction for type 2 diabetes management: a systematic review and dose-response meta-analysis of randomized controlled trials. The American Journal of Clinical Nutrition. 2022 Jul 1;116(1):40–56.

19. Hou W, Han T, Sun X, Chen Y, Xu J, Wang Y, et al. Relationship Between Carbohydrate Intake (Quantity, Quality, and Time Eaten) and Mortality (Total, Cardiovascular, and Diabetes): Assessment of 2003–2014 National Health and Nutrition Examination Survey Participants. Diabetes Care. 2022 Sep 29;45(12):3024–31.

20. Athinarayanan SJ, Adams RN, Hallberg SJ, McKenzie AL, Bhanpuri NH, Campbell WW, et al. Long-Term Effects of a Novel Continuous Remote Care Intervention Including Nutritional Ketosis for the Management of Type 2 Diabetes: A 2-Year Non-randomized Clinical Trial. Frontiers in Endocrinology [Internet]. 2019 [cited 2024 Jan 20];10. Available from: https://www.frontiersin.org/articles/10.3389/fendo.2019.00348

21. Saslow LR, Summers C, Aikens JE, Unwin DJ. Outcomes of a Digitally Delivered Low-Carbohydrate Type 2 Diabetes Self-Management Program: 1-Year Results of a Single-Arm Longitudinal Study. JMIR Diabetes. 2018 Aug 3;3(3):e9333.

 

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