There is strong evidence that weight loss improves metabolic outcomes in people with type 2 diabetes (Wilding, 2014) and weight management is the key nutritional strategy recommended by Diabetes UK. A number of different dietary strategies are commonly recommended, although there is no strong evidence to support a specific dietary regimen (NICE, 2014).
Low fat, high fibre diets (healthy eating)
Healthy eating strategies have historically been the default diet for weight loss in type 2 diabetes. Several large studies, including the Look AHEAD (Action for Health in Diabetes) study, incorporated this approach and at 10-years follow-up healthy eating (combined with increased physical activity) reduced body weight by 6%, improved glycaemic control and reduced cardiovascular (CVD) risk factors, although this did not translate to a reduction in cardiovascular events (Look AHEAD Research Group, 2013). Healthy eating diets are effective, although the concept of portion control is a key feature.
Low carbohydrate diets
Low carbohydrate diets have been promoted recently as a first-line strategy to improve weight loss and glycaemic control in people with type 2 diabetes (Feinman et al, 2015). Although low carbohydrate diets are effective for weight loss, there is no evidence for superiority compared to other strategies. In terms of glycaemic control, the evidence is conflicting, but the most recent meta-analysis states that, although low carbohydrate diets reduce HbA1c by an extra 4 mmol/mol (0.34%) in short-term studies over 3–6 months, this is not maintained at one year or later (Snorgaard et al, 2017).
Mediterranean diets
Studies demonstrate that Mediterranean diets (MD) achieve greater weight loss and greater improvement in glycaemia and CVD risk factors in people with type 2 diabetes (Esposito et al, 2015). MDs induce greater weight loss, weighted mean difference (WMD) 1.84kg and reduce HbA1c by a WMD 5mmol/mol (0.47%) when compared to other dietary strategies (Esposito et al, 2015).
Low glycaemic index (GI) diets
Meta-analyses have reported that low GI diets are not effective for promoting weight loss in people with diabetes, although they do improve glycaemic control, WMD 4 mmol/mol (0.4%) (Thomas and Elliot, 2010). However, the positive effect on glycaemic control has been questioned, with a suggestion that this is due to increased dietary fibre intake in those on low GI diets (Brand-Miller et al, 2003).
Meal replacements
Very low energy liquid diets used as total meal replacements are effective for weight loss and for reducing HbA1c in people with type 2 diabetes (Leslie et al, 2017), but require medical supervision. Partial meal replacement (PMR), using shakes, soups or bars in place of meals, has been successful in people with diabetes and evidence suggests that two rather than one PMR per day induce better outcomes (Leader et al, 2013).
Commercial programmes
Many NHS Trusts offer slimming on prescription and usually refer to established commercial groups, such as WeightWatchers, Slimming World, Rosemary Conley. Commercial groups are effective for long-term weight loss in general populations (Jolly et al, 2010), although there is little published evidence for outcomes in people with type 2 diabetes.
Intermittent fasting (5:2 diet)
Intermittent fasting (IF) involves normal eating alternated with fast days providing 500-600 Kcal/day. There are two strategies employed, either fasting on alternate days, or the more popular ‘fast diet’ involving two fast days per week (5:2). Despite the popularity of these diets, few studies have been conducted and none in people with type 2 diabetes.
Summary
There are a variety of strategies that can be used to induce weight loss in people with diabetes. Evidence suggests that significant weight losses occur with most diets and that differences between diets are small and insignificant (Johnston et al, 2014). To optimise weight loss, it is recommended that health professionals support people with diabetes with a dietary strategy of their choice and agree realistic weight loss targets.
References
Brand-Miller J, Hayne S, Petocz P, Colagiuri S (2003) Low-glycemic index diets in the management of diabetes: a meta-analysis of randomized controlled trials. Diabetes Care 26: 2261–7
Esposito K, Maiorino MI, Bellastella G et al (2015) BMJ Open 5: e008222
Feinman RD, Pogozelski WK, Astrup A et al (2015) Dietary carbohydrate restriction as the first approach in diabetes management: critical review and evidence base. Nutrition 31: 1–13
Johnston BC, Kanters S, Bandayrel K et al (2014) Comparison of weight loss among named diet programs in overweight and obese adults: a meta-analysis. JAMA 312: 923–33
Jolly K, Daley A, Adab P et al (2010) A randomised controlled trial to compare a range of commercial or primary care led weight reduction programmes with a minimal intervention control for weight loss in obesity: the Lighten Up trial. BMC Public Health 10: 439
Leader NJ, Ryan L, Molyneaux L, Yue DK (2013) Obesity (Silver Spring) 21: 251–3
Leslie WS, Taylor R, Harris L, Lean ME (2017) Int J Obes (Lond) 41: 96–101
AHEAD Research Group (2013) Cardiovascular effects of intensive lifestyle intervention in type 2 diabetes. N Engl J Med 369: 145–54
NICE (2014) Obesity: identification, assessment and management. CG189. NICE, London
Snorgaard O, Poulsen GM, Andersen HK, (2017) BMJ Open Diabetes Res Care 5: e000354
Thomas DE, Elliott EJ (2010) Br J Nutr 104: 797–802
Wilding, JPH (2014) The importance of weight management in type 2 diabetes mellitus. Int J Clin Pract 68: 682–91
This site is intended for healthcare professionals only
