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National Collaborating Centre for Chronic Conditions (UK). Type 2 Diabetes: National Clinical Guideline for Management in Primary and Secondary Care (Update). London: Royal College of Physicians (UK); 2008. (NICE Clinical Guidelines, No. 66.)

  • This publication is provided for historical reference only and the information may be out of date.

This publication is provided for historical reference only and the information may be out of date.

6Lifestyle management/non-pharmacological management

6.1. Dietary advice

6.1.1. Clinical introduction

All people with Type 2 diabetes should be supported to:

  • try to achieve and maintain blood glucose levels and blood pressure in the normal range or as close to normal as is safely possible
  • maintain a lipid and lipoprotein profile that reduces the risk of vascular disease.

Optimal dietary behaviours can contribute to all of these.

Dietary intervention should address the individual’s nutritional needs, taking into account personal choices, cultural preferences and willingness to change, and to ensure that quality of life is optimised. It is usual that a registered dietician plays a key role in providing nutritional care advice within the multidisciplinary diabetes team. It is also recognised that all team members need to be knowledgeable about nutritional therapy, and give emphasis to consistent dietary and lifestyle advice.11

The management of obesity is not specifically addressed in the current guideline. Readers are referred to the NICE obesity management guideline which addresses the area in some detail.12

Smoking cessation is not addressed in the current guideline. Readers are referred to the NICE public health programme guidance on smoking cessation services, including the use of pharmacotherapies, in primary care, pharmacies, local authorities and workplaces, with particular reference to manual working groups, pregnant smokers and hard to reach communities. Guidance was published in February 2008.

Clinical questions arise around the optimal strategies to reduce calorie intake (and thus improve sensitivity to endogenous insulin), to control exogenous delivery of free sugars into the circulation, to control blood pressure, and to optimise the blood lipid profile. Issues specifically related to people with kidney disease or of medical use of fish oils are not considered in this section. Issues specifically related to delivery of patient education are considered in the chapter on Patient Education (see chapter 5).

6.1.2. Methodological introduction

The search attempted to identify RCTs and observational studies conducted in adults with Type 2 diabetes which were assessing different forms of dietary advice targeting weight loss. A sample size threshold of N=50 and a follow-up of at least 3 months were established as cut-off points. Studies evaluating purely pharmacological interventions for weight reduction were excluded.

There were only eight studies that addressed this question.13–20 Two RCTs were excluded due to methodological limitations.* In all the studies, the intent was for participants to lose weight and thereby improve glycaemic, lipid and blood pressure control.** Among the remaining six studies there were four RCTs and two observational studies. No major methodological limitations were identified across these studies.

RCTs

One RCT17 compared the effects of a combined intervention; low-calorie diet, sibutramine therapy and meal replacements with an individualised reduced calorie diet, and was the only study to include the use of weight-loss medication.

Two RCTs used the American Diabetes Association (ADA) guidelines as a comparison group to either a soy-based meal replacement intervention,13 N=104 with a 1-year follow-up, or a low-fat vegan diet,14 N=99 with a 22-week follow-up.

A further RCT compared a low-fat with a low-carbohydrate diet.16

Observational studies

A case series with a follow-up of 6.5 years investigated the onset of diabetic complications and adherence to ADA recommendations.19 A prospective cohort study addressed the relationship between eating habits and long-term weight gain, following a group of patients being managed in primary care for a period of 4 years.20

It should be noted that the results of diet interventions aimed at patients with Type 2 diabetes are difficult to interpret due to differences in the interventions, the populations, the study designs and the outcomes reported.

As is obvious, isolated diet interventions without adequate educational support and concomitant lifestyle changes are very unlikely to reduce risk factors and to improve clinical outcomes and quality of life for patients with Type 2 diabetes.

6.1.3. Health economic methodological introduction

No health economic papers were identified.

6.1.4. Evidence statements

Weight reduction and glycaemic control outcomes

RCTs
Studies that compared a meal replacement intervention with a reduced calorie diet

An RCT comparing a soy-based meal replacement with an individualised diet based on ADA recommendations in obese Type 2 diabetics13 found that average weight reduction in the meal replacement group was greater than that in the individualised diet group. At 6 months, the meal replacement group had lost on average 5.24±0.60 kg, and the individualised diet group had lost an average of 2.85±0.67 kg (p=0.0031). At 1 year this difference was not significant with the meal replacement group losing on average 4.35±0.81 kg and the individualised diet group losing an average of 2.36±0.76 kg (p=0.0670). Level 1+

The same RCT reported that similar changes were observed in the body mass index (BMI) at 12 months with a reduction of 1.47±0.27 kg/m2 in the meal replacement group and 0.77±0.25 kg/m2 in the individualised diet group. Although these values were significantly different from their baseline values, none were significantly different from each other (p=0.0687). Level 1+

With respect to glycaemic control, the RCT found that mean HbA1c levels were significantly lower in the meal replacement than in the individualised diet group, 0.49±0.22% (p=0.0291), for the entire study period. Plasma glucose concentrations were significantly lower in the meal replacement group than in the individualised diet group at 3 (p=0.04) and 6 (p=0.002) months, but not at 12 months (p=0.595). Level 1+

The study by Redmon17 reported on a combination intervention including sibutramine, an intermittent low-calorie diet with the use of meal replacements for 1 week every 2 months, and the use of meal replacements between the low-calorie diet weeks. The comparison group received an individualised diet plan with a 500–1,000 kcal energy deficit per day.

The study reported that at 1 year of follow-up, the combination therapy group had a significantly greater weight loss of 7.3±1.3 kg than the standard therapy group 0.8±0.9 kg (p<0.001), with most weight loss occurring during the low-calorie weeks and some weight gain occurring in between the low-calorie weeks. Level 1+

In relation to glycaemic control, the study showed that at 1 year, HbA1c had declined from a baseline of 8.1±0.2% to 7.5±0.3% in the combination therapy group but had remained unchanged at 8.2±0.2% in the standard therapy group, and this difference was significant (p=0.05). After adjusting for medication changes, this difference remained significant. In an analysis of those participants whose medication had not changed, it was found that there was a significant positive linear association between change in weight at 1 year and change in HbA1c (r=0.53; p=0.006). A 5 kg decrease in weight at 1 year was associated with a 0.4% decrease in HbA1c. Level 1+

Studies comparing a low-carbohydrate with a low-fat diet

One RCT16 examined the short-term effects, participants were followed up for 3 months, of a low-carbohydrate diet compared with a reduced portion low-fat diet in obese Type 2 diabetics. There was a significantly larger mean weight reduction in the low-carbohydrate arm (N=51) of their RCT, 3.55±0.63 kg, than in the low-fat arm (N=51) which showed a mean reduction of 0.92±0.40 kg (p=0.001). Level 1+

The same RCT reported that glycaemic control improved in both arms of the trial. Improvements were greater in the low-carbohydrate arm, HbA1c decreased from a baseline of 9.00±0.20%, by 0.55±0.17%, but this did not reach statistical significance. In the low-fat arm HbA1c decreased from a baseline of 9.11±0.17% by 0.23±0.13% (p=0.132). Level 1+

Studies comparing low- or modified-fat diets with reduced calorie diets

Barnard et al.14 investigated the effects of a low-fat vegan diet compared with a diet based on ADA guidelines, on body weight and glycaemic control in an RCT with 99 Type 2 diabetics, followed up for 22 weeks. During the study period, 43% (21/49) of vegan participants and 26% (13/50) of ADA participants reduced their diabetic medications, mainly as a result of hypoglycaemia. Eight per cent in each group, 4/49 of the vegan group and 4/50 of the ADA group, increased their medications.

The study concluded that for the whole sample, body weight was reduced in both groups by 5.8 kg in the vegan group and 4.3 kg in the ADA group, but this difference was not statistically significant (p=0.082). In those whose medication was stable this difference was significant with a 6.5 kg reduction in the vegan group, and 3.1 kg in the ADA group, p<0.001. BMI declined by 2.1±1.5 kg/m2 in the vegan group and by 1.5±1.5 kg/m2 in the ADA group (p=0.08). The waist-to-hip ratio declined in the vegan group 0.02±0.01 but not in the ADA group (p=0.003). Level 1+

With respect to glycaemic control, the RCT stated that while the HbA1c decline in both groups was statistically significant from their baseline values with a decline of 0.96% (p<0.0001) in the vegan group and 0.56% (p=0.0009) in the ADA group, there was no significant difference between the groups (p=0.089). Again the results were different in those participants whose medication was unchanged. The HbA1c decline was greater in the vegan group, 1.23±1.38%, than in the ADA group, 0.38±1.11%, (p=0.01). Level 1+

Table 6.1Summarised results for body weight reduction and glycaemic control across RCTs

RCTsT=ComparisonComparisonWeight/BMIGlycaemic control
Li (2005)131 yearSoy-based meal replacementIndividualised dietWeight and BMI=NSHbA1c significantly lower in meal replacement arm
Redmon (2003)171 yearSibutramine + low-calorie diet + meal replacementIndividualised dietWeight reduction significantly higher in combination armHbA1c significantly lower in combination arm*
Daly (2006)163 monthsLow-carbohydrate dietReduced portion low-fat dietWeight reduction significantly higher in carbohydrate armHbA1c=NS
Barnard (2006)1422 weeksLow-fat vegan dietDiet based on ADA guidelinesWeight=NSHbA1c=NS
*

A 5 kg decrease in weight at 1 year was associated with a 0.4% decrease in HbA1c.

Observational studies

In an observational study with 4 years of follow-up,20 the authors investigated the association between eating behaviour and long-term weight gain. Ninety-seven Type 2 diabetics were recruited at diagnosis and after initial nutrition advice were followed up for a period of 4 years.

The study found that at the end of follow-up, mean body weight change in men was a gain of 1.3±5.4 kg, whereas in women, there was a mean body weight reduction of −1.1±5.0 kg. These changes were not statistically significant, (p values not given). Similarly, BMI increased in men by 0.42±1.76 kg/m2 and decreased in women by 0.40±1.89 kg/m2, (p values not given). Glycaemic outcomes were not reported. Level 2+

In the second observational study,19 weight loss over the 6.5-year follow-up is not reported. However, metabolic control did improve in patients over the period, with the proportion of patients with HbA1c <7% increasing from 52.4% to 64.3% in men and from 43.9 to 50.9% in women. It was not reported whether or not this was significant. Level 3

Blood pressure and blood lipid control outcomes

RCTs
Studies that compared a meal replacement intervention with a reduced calorie diet

The RCT by Li et al.,13 reporting on the comparison of a soy-based meal replacement plan with an individualised diet plan, did not report on changes in blood pressure during the study.

For the blood lipid control outcomes, while there were no significant differences between groups during the study for lipid parameters, there were differences within the groups when compared to baseline values. In the meal replacement group, there were decreases in total cholesterol, triglycerol, low-density lipoprotein (LDL) and high-density lipoprotein (HDL) at the end of the study, however these changes were only significant in the triglycerol group with an overall decrease from baseline of 28.00 mg/dl (p=0.038). Decreases in total cholesterol were significant at 3 (p<0.0001) and 6 (p=0.0037) months, but at 12 months with a reduction of 10.76 mg/dl from baseline, this was not significant (p=0.084). LDL decreased by 11.04 mg/dl at 3 months (p=0.024), but at 12 months the change from baseline had reduced to 6.10 mg/dl (p=0.255). HDL had decreased by 0.97 mg/dl at 12 months (p=0.345). In the individualised diet plan group, after initial decreases at 3 or 6 months, at 12 months there were increases in total cholesterol by 5.26 mg/dl (p=0.396), LDL by 8.76 mg/dl (p=0.129) and HDL by 2.26 mg/dl (p=0.012). Only in triglycerol levels was there a sustained decreased at 12 months with a reduction from baseline of 28.89 mg/dl (p=0.119). Level 1+

In the study by Redmon17 which compared a combined intervention (described above) with an individualised diet plan, at 1 year there were reductions in systolic and diastolic blood pressure in both groups, although this did not differ between the groups. Systolic blood pressure reduced in the combination group by 6±3 mmHg and by 6±2 mmHg in the comparison group. Diastolic blood pressure reduced in the combination group by 3±1 mmHg and by 6±2 mmHg in the comparison group. Level 1+

At 1 year, changes in fasting cholesterol, HDL, LDL and fasting triglycerides did not differ between groups. There were reductions from baseline values in fasting cholesterol and LDL cholesterol in both groups, with a decrease in fasting cholesterol of 6±8 mg/dl in the combination therapy group and 17±9 mg/dl in the comparison group (p=0.90). LDL decreased by 12±5 mg/dl in the combination therapy group and 13±6 mg/dl in the comparison group (p=0.89). Fasting triglycerides decreased by 46±24 mg/dl in the combination group compared to an increase of 8±18 mg/dl in the comparison group, however this was not significant (p=0.07). Level 1+

Studies comparing a low-carbohydrate with a low-fat diet

At 12 weeks of follow-up, in the low-carbohydrate arm of this RCT16 there was a reduction in systolic blood pressure of 6.24±2.96 mmHg and a reduction of 0.39±2.64 mmHg in the low-fat arm, with no significant difference between the arms (p=0.147). Level 1+

With respect to lipid parameters, there was a greater reduction in the total cholesterol: HDL ratio in the low-carbohydrate arm, mean reduction of 0.48, than in the low-fat arm, mean reduction 0.10 (p=0.011). There were also reductions in triglycerides in both arms, 0.67 mmol/l in the low-carbohydrate arm and 0.25 in the low-fat arm, which did not approach statistical significance (p=0.223). Level 1+

Studies comparing low- or modified-fat diets with reduced calorie diets

In the RCT comparing the low-fat vegan diet with the ADA diet,14,20 there were non-significant reductions in systolic and diastolic blood pressure in both groups. In the vegan group systolic blood pressure decreased by 3.8±12.6 mmHg (p<0.05) compared with baseline and in the ADA group by 3.6±13.7 mmHg from baseline, with no significant difference between the groups (p=0.93). Similarly the reduction in diastolic blood pressure was greater in the vegan group, 5.1±8.3 mmHg (p<0.0001) than in the ADA group 3.3±8.8 mmHg (p<0.05) although this was not different between groups (p=0.30). Level 1+

For the entire sample, although lipid parameters decreased significantly from baseline values, there were no significant differences between groups. Among those whose lipid controlling medications remained constant (vegan N=39/49; ADA N=41/50), total cholesterol reduced in the vegan groups by 33.5±21.5 mg/dl (p<0.0001), in the ADA group by 19.0±28.5 mg/dl (p<0.0001) and this was a significantly different between groups (p=0.01). Reductions in HDL cholesterol were not significantly different between the groups.

Reductions in non-HDL cholesterol were significantly lower than baseline in the vegan groups 27.6±21.1 mg/dl (p<0.0001) and in the ADA group 16.3±30.1 mg/dl (p<0.05), but not significantly different between the groups (p=0.05).

LDL cholesterol reduced in the vegan group by 22.6±22.0 mg/dl (p<0.0001) and in the ADA group by 10.7±23.3 mg/dl (p<0.05), and was significantly different between the groups (p=0.02). The total-to-HDL cholesterol ratio and triglyceride concentrations fell for both groups, but there was no difference between the groups. Level 1+

Table 6.2Summarised results for blood pressure and lipid levels across RCTs

RCTsT=ComparisonComparisonBlood pressureLipid levels
Li (2005)131 yearSoy-based meal replacementIndividualised dietNo changesNS differences
Redmon (2003)171 yearSibutramine + low calorie diet + meal replacementIndividualised dietNS differencesNS differences
Daly (2006)163 monthsLow-carbohydrate dietReduced portion low- fat dietNS differencesTC:HDL ratio significantly lower in carbohydrate arm
Barnard (2006)1422 weeksLow-fat vegan dietDiet based on ADA guidelinesNS differencesNS differences
Observational studies

In the observational study investigating the effect of eating behaviours on weight,20 changes in blood pressure or lipid profiles were not reported.

In the diabetes nutrition and complications trial19 changes in blood pressure were reported as the proportion of patients who had a systolic blood pressure <130 mmHg, which decreased from 28.6% at baseline to 11.9% at the end of the study. Similarly in women there was a decrease from 15.8% at baseline to 8.8% after 6.5 years. The proportion of patients with a diastolic blood pressure of <80 mmHg decreased from 26.2% to 21.4% and from 31.6% to 28.1% in men and women respectively.

In this study they reported the number of patients who were adherent to the ADA diet recommendations and were able to achieve the recommended intakes of various types of fats. They found that levels of adherence to the recommendations was low with only 26.6% of patients consuming the recommended amount of saturated fatty acids (SFAs), 13.0% consuming the recommended ≥10% of dietary energy from polyunsaturated fats, and 38.5% consuming the recommended ≥60% of dietary energy from carbohydrates and monounsaturated fats. They also estimated that 46.4% of patients consumed a ratio of polyunsaturated fatty acids (PUFAs)/SFAs >0.4 and 69% consumed a ratio of monounsaturated fats (MUFAs)/SFAs >1.5. Patients who consumed MUFAs/SFAs <1.5 had a 3.6–4.7 times greater risk of developing diabetic complications (confidence intervals (CIs) not presented). Patients who consumed PUFAs/SFAs <0.4 were 3.4–8.2 times more at risk of developing diabetic complications. Level 3

6.1.5. From evidence to recommendations

The GDG noted that there was little new evidence to warrant any change to previous views in this field. The major consensus-based recommendations from the UK and USA emphasise sensible practical implementation of nutritional advice for people with Type 2 diabetes. Other relevant NICE guidance should be considered where relevant, including clinical guideline no. 43 on the assessment and management of overweight and obesity in adults and children and clinical guideline no. 48 which gives dietary and lifestyle advice post-MI. Overlap with the NICE/RCP Type 1 diabetes guideline was noted. Management otherwise will concentrate on principles of healthy eating (essentially those for optimal cardiovascular risk protection), and reduction of high levels of free carbohydrate in food that are hyperglycaemic in the presence of defective insulin secretory reserve.

If people are currently gaining weight, weight maintenance is advantageous.

The GDG noted that in some people with Type 2 diabetes and weight problems it might be appropriate to consider pharmacotherapy, however this was not within the clinical questions addressed.

As with Patient Education (see chapter 5) delivery of dietary advice was noted to depend not only on specific skills, but also required all members of the diabetes care team to be familiar with local policy and thus delivering consistent advice.

Concerns continue to be noted over the promotion of ‘diabetic foods’ which may be low in classical sugars but high in calories and thus unsuitable as well as unnecessary for the overweight. While reduction in weight was clearly understood to be beneficial through improvements in insulin insensitivity (whether relying on endogenous or exogenous insulin), low-carbohydrate diets were noted to be of unproven safety in the long term and thus could not be endorsed. Similarly high-protein diets are acknowledged as promoting short-term weight loss, but cannot be recommend as safe in the long term.

A dietary plan for people with diabetes would follow the principles of healthy eating in the population, and thus include carbohydrate from fruits, vegetables, wholegrains, and pulses (and thus high fibre and low glycaemic index), reduction in salt intake, the inclusion of low-fat milk and oily fish, and control of saturated and trans fatty acid intake.

The importance of advice on alcohol to the overweight and to those prone to hypoglycaemia through use of insulin secretagogues or insulin was judged important.

RECOMMENDATIONS

R7.

Provide individualised and ongoing nutritional advice from a healthcare professional with specific expertise and competencies in nutrition.

R8.

Provide dietary advice in a form sensitive to the individual’s needs, culture and beliefs being sensitive to their willingness to change, and the effects on their quality of life.

R9.

Emphasise advice on healthy balanced eating that is applicable to the general population when providing advice to people with Type 2 diabetes. Encourage high-fibre, low glycaemic index sources of carbohydrate in the diet, such as fruit, vegetables, wholegrains and pulses; include low-fat dairy products and oily fish; and control the intake of foods containing saturated and trans fatty acids.

R10.

Integrate dietary advice with a personalised diabetes management plan, including other aspects of lifestyle modification, such as increasing physical activity and losing weight.

R11.

Target, for people who are overweight, an initial body weight loss of 5–10%, while remembering that lesser degrees of weight loss may still be of benefit and that larger degrees of weight loss in the longer term will have advantageous metabolic impact.

R12.

Individualise recommendations for carbohydrate and alcohol intake, and meal patterns. Reducing the risk of hypoglycaemia should be a particular aim for a person using insulin or an insulin secretagogue.

R13.

Advise individuals that limited substitution of sucrose-containing foods for other carbohydrate in the meal plan is allowable, but that care should be taken to avoid excess energy intake.

R14.

Discourage the use of foods marketed specifically for people with diabetes.

R15.

When patients are admitted to hospital as inpatients or to any other institutions, implement a meal planning system that provides consistency in the carbohydrate content of meals and snacks.

6.2. Management of depression

6.2.1. Clinical introduction

Psychological well-being is clearly part of being healthy. It is an important part of healthcare management of any condition where psychological health is impaired or where it has particular impact on clinical management.

There is evidence of a high prevalence of psychological ill-health in people with diabetes, notably for depression,21 which is often under-recognised.22 Additionally because of the importance of self-care to the management of the condition, there is evidence that psychological ill-health is associated with adverse effects on other aspects of the long-term health of people with Type 2 diabetes.23–25

Formal assessment of psychological well-being is not a standard part of practice in diabetes care in the UK. Other guidelines, including the NICE guideline for people with Type 1 diabetes, have emphasised the importance of recognising and managing depression. Only general recommendations have been made regarding being alert to problems, availability of skills to manage routine psychological disorders, and of appropriate referral to those with special expertise where the condition is more severe.26 NICE has recently published a guideline on the management of depression.27

No evidence search has been performed for the purpose of the current guideline due to the availability of the NICE depression guideline. People with Type 2 diabetes with psychological and/or depressive disorders should be identified by continuing professional awareness, and managed in accordance with current national guidelines.

Footnotes

*

One RCT comparing the effects of a high-protein with a low-protein diet15 and another RCT comparing low-carbohydrate versus conventional weight loss diets in severely obese adults.18

**

Four studies focused on the effects of diet in obese Type 2 diabetics.

Copyright © 2008, Royal College of Physicians of London.

All rights reserved. No part of this publication may be reproduced in any form (including photocopying or storing it in any medium by electronic means and whether or not transiently or incidentally to some other use of this publication) without the written permission of the copyright owner. Applications for the copyright owner’s written permission to reproduce any part of this publication should be addressed to the publisher.

Cover of Type 2 Diabetes
Type 2 Diabetes: National Clinical Guideline for Management in Primary and Secondary Care (Update).
NICE Clinical Guidelines, No. 66.
National Collaborating Centre for Chronic Conditions (UK).

NICE (National Institute for Health and Care Excellence)

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