Randomised controlled trial evaluating lifestyle interventions in people with impaired glucose tolerance

doi:10.1016/j.diabres.2005.09.018

Diabetes Research and Clinical Practice

Volume 72, Issue 2, May 2006, Pages 117-127

https://doi.org/10.1016/j.diabres.2005.09.018 Get rights and content

Abstract

Aim

To evaluate the effectiveness of lifestyle interventions in people with impaired glucose tolerance (IGT).

Methods

Participants with IGT (n = 78), diagnosed on two consecutive oral glucose tolerance tests (OGTTs), were randomly assigned to a 2-year lifestyle intervention or to a control group. Main outcome measures were changes from baseline in: nutrient intake; physical activity; anthropometry, glucose tolerance and insulin sensitivity. Measurements were repeated at 6, 12 and 24 months follow-up.

Results

After 24 months follow-up, there was a significant fall in total fat consumption (difference in change between groups (Δ intervention − Δ control) = −17.9, 95% confidence interval (CI) −33.6 to −2.1 g/day) as a result of the intervention. Body mass was significantly lower in the intervention group compared with controls after 6 months (−1.6, 95% CI −2.9 to −0.4 kg) and 24 months (−3.3, 95% CI −5.7 to −0.89 kg). Whole body insulin sensitivity, assessed by the short insulin tolerance test (ITT), improved after 12 months in the intervention group (0.52, 95% CI 0.15–0.89%/min).

Conclusions

These findings complement the findings of the Finnish Diabetes Prevention Study and the American Diabetes Prevention Study, both of which tested intensive interventions, by showing that pragmatic lifestyle interventions result in improvements in obesity and whole body insulin sensitivity in individuals with IGT, without change in other cardiovascular risk factors.

Introduction

Coronary heart disease (CHD) and Type 2 diabetes are major health problems and strategies are urgently needed to reduce cardiovascular risk in high risk individuals. It has recently been demonstrated that intensive behavioural interventions substantially lower the risk of diabetes in people with IGT [1], [2], [3], a high risk condition for the development of Type 2 diabetes and CHD [4]. However, these studies were resource intensive (e.g. providing one to one case managers) so that the effectiveness of pragmatic lifestyle interventions are not known. Additionally, it is unclear what effect lifestyle interventions have on whole body insulin sensitivity, measured directly, in people with IGT.

In this paper, we report the main outcomes after 24 months follow-up of a pragmatic randomised controlled trial (RCT) of diet and physical activity counselling for men and women with IGT, diagnosed using two consecutive oral glucose tolerance tests (OGTTs), conducted in Newcastle upon Tyne, UK. The study tested the null hypotheses that, in individuals with IGT: (i) counselling from a dietitian and physiotherapist over 24 months would result in no changes in nutrient intake and physical activity or CHD risk factors (including whole body insulin sensitivity) after 6 months follow-up; and (ii) any changes in nutrient intake and physical activity or CHD risk factors detected at 6 months would not be sustained for 24 months.

Section snippets

Study design

We conducted an RCT with one intervention and one control arm at the Royal Victoria Infirmary, Newcastle upon Tyne, UK between 1994 and 1998. Men and women of European origin, aged 24–75 years, who had IGT identified on two consecutive OGTTs, the second within 2–12 weeks of the first, were eligible to participate. Individuals who were pregnant, on therapeutic diets or unable to undertake moderate physical activity were excluded. Medications likely to interfere with glucose metabolism were

Recruitment

Fig. 1 shows the recruitment outcomes of the study. A total of 498 individuals with IGT were identified. Of these, 135 did not agree to be re-tested, 104 failed to reply and 51 were excluded. Of the remaining 208 who were re-tested 46 had diabetes, 80 were NGT and 82 were IGT. Of those with IGT, 78 were recruited and were randomised in equal numbers to the intervention group and to the control group.

Adherence to the intervention

On average, intervention participants attended 80% (range 67–95%) of review appointments in the

Changes in nutrient intake

The proportion of individuals who had met the target for a dietary fat intake of <30% total energy was higher amongst the intervention group (40%) than amongst the controls (13%) after 24 months follow-up (Table 2). Table 3, Table 4, Table 5 show that dietary fat intake decreased between baseline and 6, 12 and 24 months more in the intervention than the control group, respectively. The mean difference in change in total fat intake between groups was significant after 6 months (difference in

Interpretation

We have shown that counseling from a dietitian and physiotherapist results in important changes in CHD risk factors in people with IGT. Since starting this investigation, ‘gold standard’ diabetes prevention studies namely, the American Diabetes Prevention Study [1], Da Qing study [2], the Finnish Diabetes Prevention Study (FDPS) [3] have been conducted which tested intensive interventions in ethnically diverse groups with IGT. Our findings complement these studies because our interventions were

Limitations

Recent diabetes prevention studies [1], [2], [3] have provided strong evidence for the effectiveness of lifestyle interventions for the prevention of diabetes in people with IGT. The present study was not designed to assess the impact of counseling on health outcomes but rather on risk factors for CHD and Type 2 diabetes.

Other comparable lifestyle studies have had more intensive interventions such as 24 review appointments in the first 6 months [21] in contrast to the six appointments offered

Implications

The results of this study imply that less intensive, pragmatic interventions can reduce risk factors for CHD and Type 2 diabetes such as overweight and insulin resistance in individuals with IGT. These are evident after 6 months and are sustained at 24 months. This is important since obesity has been identified as a public health challenge in a recent White Paper in the UK [22]. However, more research is needed to determine practical ways to identify people with IGT in Primary Health Care, such

Acknowledgements

We would like to thank Mrs Karen Imrie for providing the physiotherapy intervention; Drs Mark Daly, Stuart Bennett, Kalpna Chattergee and Nick Roper for performing the short insulin tolerance tests; Mrs Pat Shearing for undertaking the biochemical assays and Dr Robert Newcombe for statistical advice. We also acknowledge the support of Mrs Linda Norris, Department of Community and Leisure Services, Newcastle upon Tyne. The study was funded by grants from the British Heart Foundation, Northern &

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Thirty articles reporting on 19 randomized controlled trials met the eligibility criteria, representing 5,172 adults. Thirteen studies (68%) showed significant improvements for the primary outcome measured. Social cognitive theory was the behavior change theory most commonly applied in interventions (n=15) with 11 finding significant intervention effects. Goal setting, problem solving, social support, and self-monitoring were the most commonly reported techniques (n=15, n=14, n=11, and n=11, respectively). Most studies had a high (n=11) or unclear (n=8) risk of bias. There was fair evidence (Grade II) supporting the use of behavior change theories to inform development of dietetics interventions.
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Randomised controlled trial evaluating lifestyle interventions in people with impaired glucose tolerance

Abstract

Aim

Methods

Results

Conclusions

Introduction

Section snippets

Study design

Recruitment

Adherence to the intervention

Changes in nutrient intake

Interpretation

Limitations

Implications

Acknowledgements

Diabetes Res. Clin. Pract.

Am. J. Clin. Nutr.

Reduction in the incidence of type 2 diabetes with lifestyle intervention or metformin

New Engl. J. Med.

Effects of diet and exercise in preventing NIDDM in people with impaired glucose tolerance. The Da Qing IGT and Diabetes Study

Diabetes Care

Prevention of type 2 diabetes mellitus by changes in lifestyle among subjects with impaired glucose tolerance

New Engl. J. Med.

Impaired glucose tolerance and impaired fasting glycaemia: the current status on definition and intervention

Diabet. Med.

The short insulin tolerance test is safe and reproducible

Diabet. Med.

Transtheoretical therapy: towards a more intregrative model of change

Psychotherapy: Theory Res. Pract.

The stages model and processes of change in dietary fat reduction

J. Nutr. Diet