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Low carbohydrate diet in type 2 diabetes

Authoring team

Low-carbohydrate, high-protein diets

Rationale for low-carbohydrate diets in patients with type 2 diabetes

  • blood glucose increases as a result of carbohydrate ingestion
    • a low-carbohydrate diet
      • results in a lowering of glycaemia and and insulin levels
        • causing an increase in circulating fatty acids that can be used as energy by the body, with the production of ketone bodies
          • researchers have stated that this diet results in weight loss and increased satiety (1)

How many carbs is low carb?

  • different investigators have used different definitions for a low-carbohydrate diet

    • the American Diabetes Association define
      • a low-carbohydrate diet contains less than 130 g carbohydrate per day (i.e. 26% of 2000 kcal diet as carbohydrate)
      • a diet with 45-26% of total energy as carbohydrate to be a moderate carbohydrate diet
      • a diet containing 30 g carbohydrate daily is considered a very low-carbohydrate ketogenic diet

    • according to Wheeler et al. (2)
      • 30-40% of calories as carbohydrate are indicative of a moderate-to-low carbohydrate diet
      • whereas a very low-carbohydrate diet contains 21-70 g of carbohydrate per day

Length of studies is generally short so long term conclusions are difficult to make based on evidence:

  • studies on the efficacy of low-carbohydrate diets in subjects with type 2 diabetes have mainly been short term and with small population sizes, although benefits have been reported, especially on weight loss

  • one year studies:

    • a one year study was undertaken by Larsen et al. recently studied two groups of adults with type 2 diabetes for 1 year
    • one group of 53 individuals was randomized to a diet high in protein (30% of total energy intake) and low glycemic index carbohydrate (40% of total energy)
    • alternative group of 46 individuals were assigned to a diet with 15% energy intake from protein and 55% energy from low glycemic index carbohydrate
    • at the end of the intervention period, there were no significant differences between the two groups in terms of weight loss, serum triacylglycerol, total cholesterol and high-density lipoprotein cholesterol levels, blood pressure and renal function

    • Krebs et al. compared a low-fat, high-protein diet (total energy comprised 30% from protein, 40% from carbohydrate and 30% from fat) to a low-fat, high-carbohydrate diet (total energy comprised 15% from protein, 55% from carbohydrate and 30% from fat)
      • a total of 419 adults with type 2 diabetes were blindly randomized to either diet.
      • after 1 year, 70% of the initial participants had completed the study, but there were no significant differences between the two groups in terms of weight loss (average of 2-3 kg), waist circumference reduction (average of 2-3 cm), HbA1c, renal function and cholesterol

  • a meta-analysis of randomized controlled trials published in 2012 (5)
    • concluded that there was no great difference in terms of weight loss between a low-carbohydrate diet high in protein and an isocaloric diet with moderate protein

  • a sixth month study showed that a low-carbohydrate diet was effective in lowering the HbA1c and triglyceride levels in patients with type 2 diabetes who are unable to adhere to a calorie-restricted diet (6)

Ketogenic diets:

  • benefits of ketogenic diets on glycemic control were reviewed by Paoli et al (7)
    • majority of studies claimed an improvement in glycemic control and a reduction in medication with this diet
    • however, studies on ketogenic diets are few, and this area requires further investigation

Notes:

  • critics of this type of a low carbohydrate diet argue that less carbohydrate usually results in an increase in the proportion of saturated fatty acids in the diet, with associated negative effects on cardiovascular disease (8)
    • however, others (9) have suggested that low-carbohydrate diets lower glycaemia, reducing the need for medication that, in turn, decreases the risk of hypoglycaemia (correlated with a high risk of morbidity and mortality), which favours weight loss

Reference:

  • 1)Adam-Perrot A, Clifton P, Brouns F. Low-carbohydrate diets: nutritional and physiological aspects. Obes Rev 2006; 7(1): 49-58.
  • 2) Wheeler ML, Dunbar SA, Jaacks LM, et al. Macronutrients, food groups, and eating patterns in the management of diabetes: a systematic review of the literature. 2010; Diabetes Care 2012; 35(2): 434-45. Correction in: Diabetes Care 2012; 35(6): 1395.
  • 3) Larsen RN, Mann NJ, Maclean E, Shaw JE. The effect of high-protein, low-carbohydrate diets in the treatment of type 2 diabetes: a 12-month randomized controlled trial. Diabetologia 2011; 54(4): 731-40.
  • 4) Krebs JD, Elley C-R, Parry-Strong A, et al. The diabetes excess weight loss (DEWL) trial: a randomized controlled trial of high-protein versus high-carbohydrate diets over 2 years in type 2 diabetes. Diabetologia 2012; 55(4): 905-14.
  • 5) Wycherley TP, Moran LJ, Clifton PM, Noakes M, Brinkworth GD. Effects of energy-restricted high-protein, low-fat compared with standard-protein, low-fat diets: a meta-analysis of randomized controlled trials. Clin Nutr 2012; 96(6): 1281-98.
  • 6)Yamada Y et al. A non-calorie-restricted low-carbohydrate diet is effective as an alternative therapy for patients with type 2 diabetes. Intern Med. 2014;53(1):13-9.
  • 7)Paoli A, Rubini A, Volek JS, Grimaldi KA. Beyond weight loss: a review of the therapeutic uses of very-low-carbohydrate (ketogenic) diets. Eur J Clin Nutr 2013; 67(8): 789-96.
  • 8) Feinman RD, Volek JS. Carbohydrate restriction as the default treatment for type 2 diabetes and metabolic syndrome. Scand Cardiovasc J 2008; 42(4): 256-63.
  • 9) Westman EC, Vernon MC. Has carbohydrate-restriction been forgotten as a treatment for diabetes mellitus? A perspective on the ACCORD study design. Nutr Metab (Lond) 2008; 9: 5-10.
  • 10) Khazrai YM et al.Effect of diet on type 2 diabetes mellitus: a review. Diabetes Metab Res Rev. 2014 Mar;30 Suppl 1:24-33.

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