Low carbohydrate diet in type 2 diabetes

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.