Snorgaard O, Poulsen GM, Andersen HK, Astrup A. Systematic review and meta-analysis of dietary carbohydrate restriction in patients with type 2 diabetes. BMJ Open Diabetes Res Care. 2017;5(1). doi:10.1136/bmjdrc-2016-000354
McArdle PD, Greenfield SM, Rilstone SK, Narendran P, Haque MS, Gill PS. Carbohydrate restriction for glycaemic control in Type 2 diabetes: a systematic review and meta-analysis. Diabet Med. 2019;36(3):335-348. doi:10.1111/dme.13862
Sainsbury E, Kizirian N V., Partridge SR, Gill T, Colagiuri S, Gibson AA. Effect of dietary carbohydrate restriction on glycemic control in adults with diabetes: A systematic review and meta-analysis. Diabetes Res Clin Pract. 2018;139:239-252. doi:10.1016/j.diabres.2018.02.026
Salas-Salvadó J, Becerra-Tomás N, Papandreou C, Bulló M. Dietary Patterns Emphasizing the Consumption of Plant Foods in the Management of Type 2 Diabetes: A Narrative Review. Adv Nutr. 2019;10:S320-S331. doi:10.1093/advances/nmy102
Huo R, Du T, Xu Y, et al. Effects of Mediterranean-style diet on glycemic control, weight loss and cardiovascular risk factors among type 2 diabetes individuals: A meta-analysis. Eur J Clin Nutr. 2015;69(11):1200-1208. doi:10.1038/ejcn.2014.243
Seckold R, Fisher E, de Bock M, King BR, Smart CE. The ups and downs of low-carbohydrate diets in the management of Type 1 diabetes: a review of clinical outcomes. Diabet Med. 2019;36(3):326-334. doi:10.1111/dme.13845
Turton JL, Raab R, Rooney KB. Low-carbohydrate diets for type 1 diabetes mellitus: A systematic review. de Souza RJ, ed. PLoS One. 2018;13(3):e0194987. doi:10.1371/journal.pone.0194987
de Bock M, Lobley K, Anderson D, et al. Endocrine and metabolic consequences due to restrictive carbohydrate diets in children with type 1 diabetes: An illustrative case series. Pediatr Diabetes. 2018;19(1):129-137. doi:10.1111/pedi.12527
Bolla AM, Caretto A, Laurenzi A, Scavini M, Piemonti L. Low-carb and ketogenic diets in type 1 and type 2 diabetes. Nutrients. 2019;11(5). doi:10.3390/nu11050962
Facilitating Behavior Change and Well-being to Improve Health Outcomes: Standards of Medical Care in Diabetes-2020. Diabetes Care. 2020;43:S48-S65. doi:10.2337/dc20-S005
Dyson PA, Twenefour D, Breen C, et al. Diabetes UK evidence-based nutrition guidelines for the prevention and management of diabetes. Diabet Med. 2018;35(5):541-547. doi:10.1111/dme.13603
Diabetes Australia. Low Carbohydrate Eating for People with Diabetes Position Statement.; 2018. https://www.diabetesaustralia.com.au/position-statements. Accessed February 4, 2020.
Diabetes UK. Position Statement: Low-Carb Diets for People with Diabetes.; 2017. https://www.diabetes.org.uk/professionals/position-statements-reports/food-nutrition-lifestyle/low-carb-diets-for-people-with-diabetes. Accessed February 4, 2020.
de Koning L, Fung TT, Liao X, et al. Low-carbohydrate diet scores and risk of type 2 diabetes in men. Am J Clin Nutr. 2011;93(4):844-850. doi:10.3945/ajcn.110.004333
Noto H, Goto A, Tsujimoto T, Noda M. Low-carbohydrate diets and all-cause mortality: a systematic review and meta-analysis of observational studies. PLoS One. 2013;8(1):e55030. doi:10.1371/journal.pone.0055030
Adeva-Andany MM, González-Lucán M, Fernández-Fernández C, Carneiro-Freire N, Seco-Filgueira M, Pedre-Piñeiro AM. Effect of diet composition on insulin sensitivity in humans. Clin Nutr ESPEN. 2019;33:29-38. doi:10.1016/j.clnesp.2019.05.014
Riserus U. Fatty acids and insulin sensitivity. Curr Opin Clin Nutr Metab Care. 2008;11(2):100-5. doi: 10.1097/MCO.0b013e3282f52708.
Riserus U, Willett WC, Hu FB. Dietary fats and prevention of type 2 diabetes. Prog Lipid Res. 2009;48(1):44-51. Epub 2008 Nov 7.
Rivellese AA, Lilli S. Quality of dietary fatty acids, insulin sensitivity and type 2 diabetes. Biomed Pharmacother. 2003;57(2):84-87. doi:10.1016/S0753-3322(03)00003-9
Haag M, Dippenaar NG. Dietary fats, fatty acids and insulin resistance: short review of a multifaceted connection. Med Sci Monit. 2005;11(12):RA359-67. Epub 2005 Nov 24.
Brinkworth GD, Noakes M, Clifton PM, Bird AR. Comparative effects of very low-carbohydrate, high-fat and high-carbohydrate, low-fat weight-loss diets on bowel habit and faecal short-chain fatty acids and bacterial populations. Br J Nutr. 2009;101(10):1493-1502. doi:10.1017/S0007114508094658
Russell WR, Gratz SW, Duncan SH, et al. High-protein, reduced-carbohydrate weight-loss diets promote metabolite profiles likely to be detrimental to colonic health. Am J Clin Nutr. 2011;93(5):1062-1072. doi:10.3945/ajcn.110.002188
Agans R, Gordon A, Kramer DL, Perez-Burillo S, Rufián-Henares JA, Paliy O. Dietary fatty acids sustain the growth of the human gut microbiota. Appl Environ Microbiol. 2018;84(21). doi:10.1128/AEM.01525-18
David LA, Maurice CF, Carmody RN, et al. Diet rapidly and reproducibly alters the human gut microbiome. Nature. 2014;505(7484):559-563. doi:10.1038/nature12820
Hayami T, Kato Y, Kamiya H, et al. Case of ketoacidosis by a sodium-glucose cotransporter 2 inhibitor in a diabetic patient with a low-carbohydrate diet. J Diabetes Investig. 2015;6(5):587-590. doi:10.1111/jdi.12330
Yabe D, Iwasaki M, Kuwata H, et al. Sodium-glucose co-transporter-2 inhibitor use and dietary carbohydrate intake in Japanese individuals with type 2 diabetes: A randomized, open-label, 3-arm parallel comparative, exploratory study. Diabetes, Obes Metab. 2017;19(5):739-743. doi:10.1111/dom.12848
The facts on low-carb high-fat diets and diabetes
Low-carbohydrate diets, including low carbohydrate high fat (LCHF) and ketogenic (keto) diets have been gaining popularity among people with diabetes, as a way of managing blood glucose levels and weight. But are they really the answer to optimal diabetes management?
There’s no formal definition of low carb. This term can be used for diets as low as 20g of carbs per day or for those with a more modest reduction in carbs (less than 45% of total energy intake).
What is a low-carb diet?
Low carb and very low-carb diets typically restrict or exclude a wide range of foods including wholegrains, starchy vegetables, legumes, most fruits and some dairy foods and replacing them with non-starchy vegetables, meat, poultry, seafood, eggs, olive oil, coconut oil, nuts, and dairy foods such as cheese, butter, cream and Greek yoghurt. They often encourage choosing higher fat cuts of meat and full-fat dairy foods.
When we eat carbohydrate, it is broken down during digestion to glucose, which then appears in the bloodstream. It might therefore seem logical that reducing carbohydrate intake will help to lower blood glucose levels. And to some extent, this is the case.
Is a low-carb diet the best way to manage my diabetes?
But if you have type 2 diabetes, the reason you don’t deal with carbs in the same way as someone without diabetes is because of the underlying insulin resistance. This means that any dietary or lifestyle changes you make should be aimed at improving how insulin works in your body – treating the underlying problem of insulin resistance rather than just the symptoms of high blood glucose.
Some diets that help you to lose weight may improve insulin resistance and lower blood glucose levels. Low-carb diets are no exception and evidence shows that low-carb diets (including very low-carb diets) can help improve blood glucose levels and blood fats and help reduce medication needs in people with type 2 diabetes. But other diets, including Mediterranean and low-fat vegetarian diets, have shown similar benefits. This suggests that low-carb diets are not the only option and that cutting carbs isn’t necessary for managing diabetes.
How does a low-carb diet affect type 2 diabetes?There is evidence that low-carb diets, particularly those high in animal foods, can worsen insulin sensitivity, increase the risk of type 2 diabetes and increase overall mortality. Diets high in saturated fat are associated with increased insulin resistance and risk of type 2 diabetes. And restricting carbohydrate intake and consuming more fat and protein, particularly from animal sources, can cause negative changes in gut bacteria, potentially increasing inflammation and risk of digestive diseases including bowel cancer (32–35).
There is a lack of research to tell us whether low-carbohydrate diets are safe and effective for people with type 1 diabetes.
Current recommendations on low-carb diets for diabetesDiabetes Australia, the American Diabetes Association and Diabetes UK have all published recommendations on the use of low-carbohydrate diets for people with diabetes. They state that while there is evidence for short-term benefits of low-carb diets for type 2 diabetes, in the long run (12 months or more) they appear no more effective than higher carbohydrate eating patterns. They also point out research to suggest that low-carb diets are hard to sustain –an important consideration when making dietary changes to optimise your health.
- The American Diabetes Association says that low-carb diets are not appropriate for certain groups including women who are pregnant or lactating, children and those with renal disease or disordered eating behaviour.
- Diabetes UK also caution against children eating a low-carb diet because of serious concerns about the impact on growth and Australian researchers found that this diet can affect the growth of children with type 1 diabetes.
- Diabetes Australia recommend that people with diabetes who wish to follow a low-carb diet should do so in consultation with their diabetes healthcare team, including seeking advice from an Accredited Practising Dietitian experienced in diabetes management.
Different research show that there are many carbs that shouldn’t feature regularly in a healthy diet. These include refined starches (such as biscuits, cakes, pastries, highly processed breakfast cereals and white bread) and added sugars (such as confectionary and soft drinks). It’s likely that most of the short-term benefits of going low carb come from eliminating these foods from your diet.
The pros and cons of going low carb
However, low-carb diets also restrict most of the foods we know are beneficial for good health including wholegrains, legumes, fruits and some vegetables. Research has shown that eating more of these foods is associated with a reduced risk of many chronic diseases including cardiovascular disease, type 2 diabetes and some types of cancer. The long-term effects of following a low-carb diet are unknown, but this type of eating plan is very different to the diets of long-lived healthy populations, who all consume a mostly plant-based diet.
Low-carb diets can also have some unpleasant side effects including constipation, bad breath, headaches and dehydration because of ketosis (breaking down fat for energy). Low-carb diets can also lead to poor energy levels and fatigue, making exercise difficult, particularly endurance exercise.
A word of caution about diabetes medications and low-carb dietsIf you choose to follow a low-carb diet and you are taking insulin or some types of oral medications, it is important that you see your doctor before changing your diet. A low-carb diet can increase the risk of hypos if you are taking insulin or sulphonylureas and your medication doses will need adjusting.
Another type of diabetes medication, called sodium-glucose co-transporter-2 inhibitors (abbreviated to SGLT2i) has been found to cause a serious condition called diabetic ketoacidosis (DKA) in some people, particularly when they restrict their carbohydrate or overall food intake. So make sure to check in with your doctor beforehand as you will likely need to stop taking this medication if you adopt a low carb eating plan.
In summaryLow-carb diets are one way to lose weight and improve blood glucose levels, at least in the short term, but they are not the only way and may come with longer-term health risks.
There are certainly benefits of cutting down on refined starches and added sugars – few people would argue with this. But there’s also good evidence for the health benefits of many quality carbohydrate foods including legumes, wholegrains, fruit and vegetables, and research points towards a plant-based diet being one of the best types of eating plans for long-term health and chronic disease prevention.
If you choose to follow a low-carb diet, try to choose more plant-based sources of protein and fat (including avocado, nuts, seeds, olive oil, tofu and tempeh), and fill up on plenty of non-starchy vegetables and salads.
For more information on managing diabetes, check out our fact sheet. Consult with your doctor or health care professional for further advice.