Type 2 diabetes - a population health problem
The rapid increase in the prevalence of type 2 diabetes, obesity and associated complications is a major public health problem. In Australia, data from the 1999-2000 AusDiab study estimated that approximately 1 million (7.4%) Australian adults aged 25 years and over have type 2 diabetes [
1], with approximately 85% being overweight or obese [
2]. The growing epidemics of type 2 diabetes and obesity have been concurrent, with the prevalence of both doubling over the past 20 years [
1]. The prevalence of type 2 diabetes is predicted to increase dramatically over the next few decades; projections are that by 2030, 8.4% Australian adults aged 20-79 will have the disease [
3]. Similar rapidly increasing prevalence estimates have been reported for the UK [
3], USA [
3,
4] and other developed and developing countries [
3].
Identified as the seventh leading cause of death among Australian adults, type 2 diabetes is a major cause of premature mortality and morbidity due to cardiovascular, renal, ophthalmic and neurological disease [
5]. Data from the DiabCost Australia study, which assessed the total costs of type 2 diabetes to the health care system, society, government and carers, estimated that $3 billion a year is spent treating type 2 diabetes [
6]. Since the burden of illness associated with type 2 diabetes increases with the onset of microvascular and macrovascular complications [
6], there is high priority for effective and sustainable strategies to slow or prevent the onset of complications. The value of achieving glycaemic control is underscored by the landmark findings of the UK Prospective Diabetes Study, a 10 year observational follow-up in patients with diabetes, whereby each 1% reduction in glycosylated haemoglobin (HbA1c) was associated with a 14% reduction in myocardial infarction, a 37% reduction in microvascular events, and a 21% reduction in diabetes-related mortality [
7]. This is of particular importance for people with type 2 diabetes since coronary heart disease is responsible for about 70% to 80% of deaths in this population [
8].
Lifestyle factors that adversely affect energy balance (physical inactivity and over-nutrition) play a major role in the development of both type 2 diabetes and obesity [
9,
10]. The importance of weight management, by means of a healthy, energy-restricted diet and a physically active lifestyle, is considered to be the primary approach in the treatment of overweight and obesity [
11,
12] and is widely acknowledged as a cornerstone of the management of type 2 diabetes and its related morbidities [
13]. There is also evidence that many of the traditional pharmacologic approaches frequently used to treat diabetes contribute to weight gain [
14]. Weight loss or weight management is an important therapeutic task for most people with type 2 diabetes, not only for improved glycaemic control but also for reducing cardiovascular disease (CVD) risk [
13]. A modest weight loss of 5-10% of body weight has been associated with improvements in fasting plasma glucose, HbA1c, insulin, lipid levels, and blood pressure [
10]. In addition, there is compelling epidemiologic and experimental evidence that physical activity confers substantial protection against CVD and premature mortality in those with type 2 diabetes, independent of weight loss, through its favourable effects on blood pressure, blood glucose, insulin sensitivity, lipid profile, fibrinolysis, endothelial function and inflammatory defence systems [
15,
16].
At present in Australia, type 2 diabetes is managed primarily in the general practice setting (primary care). In addition to medication management and monitoring of glycaemic control, this may include brief lifestyle advice from General Practitioners (GPs), and for some, a Diabetes Care Plan that includes referral for a limited number of visits to diabetes educators, dietitians, exercise physiologists and other allied health professionals. Given the challenge of health behaviour change and weight loss, and the need for ongoing assistance to maintain such changes, approaches that work in concert with primary care are needed, with such approaches involving more behaviourally-focussed and longer-term self-management supports [
17].
Lifestyle management and weight loss intervention trials in type 2 diabetes
There is a large literature on lifestyle management and weight loss interventions in type 2 diabetes, including the current landmark Look AHEAD trial, which is evaluating an intensive four-year weight loss intervention to reduce cardiovascular morbidity and mortality [
18,
19]. Across numerous studies, there is clear evidence that intensive lifestyle interventions involving reduced energy (and fat) intake, regular physical activity, cognitive behaviour therapy and frequent participant contact will produce significant behavioural improvements, as well as weight loss (5-7% of body weight) and concomitant improvements in glycaemic control and dyslipidaemia [
10,
20,
21]. However, there are a number of gaps in this literature that make its findings less relevant to informing a population-based approach to the lifestyle management of type 2 diabetes. First, the majority of trials have evaluated intensive, clinic-based interventions that are similar to the diabetes education programs offered through hospitals as part of clinical management. While these clinic-based interventions are effective [
22], few patients with type 2 diabetes take part in such programs [
23]. Second, very few studies include a post-intervention follow-up assessment to determine whether improvements are maintained longer term [
24,
25].
Broad reach weight loss and lifestyle intervention trials
A number of recent studies have evaluated weight loss interventions delivered via telephone, tailored print and the internet [
26‐
31]. Of note are two recent studies which have evaluated a telephone-delivered approach for initiation and maintenance of weight loss [
29,
31]. One study observed similar short-term weight loss at 6-months for both face-to-face (8.9%) and telephone-delivered (7.7%) interventions [
29]. In the other trial, following initial weight loss at 6 months, small but statistically non-significant regain in weight was observed for those in the 12-month telephone and face-to-face maintenance contact groups, which was significantly less than the regain observed in the control group [
31].
Telephone-delivered interventions have the potential for widespread and cost-effective population reach, and have been widely researched [
32‐
38]. A systematic review of 26 telephone-delivered physical activity and dietary behaviour intervention studies found very strong support for their efficacy to produce short-term behavioural changes in both people with and without chronic conditions, with 20 of 26 studies reporting significant behavioural improvements immediately post-intervention [
39]. Interventions lasting six to 12 months and those including 12 or more calls produced the most favourable outcomes. Our own work in this area has shown telephone-delivered interventions to be effective in promoting both initiation and maintenance [
40,
41] of dietary change, as well as demonstrating cost-effectiveness [
42].
Purpose
This paper describes the methods of the Living Well with Diabetes trial which is evaluating a telephone-delivered behavioural weight loss intervention focussing on physical activity, diet and behavioural therapy in adults with type 2 diabetes. To promote maintenance the 18 month intervention has an intensive first 6 months focussed on initiation of behaviour change, followed by 12 months focussed on enhancing/supporting maintenance. Measurement at baseline, six, 12, 18, and 24 months allows for assessment of initiation and maintenance of change - a major contribution of the study to the evidence base on broad reach interventions to support weight loss and lifestyle management in type 2 diabetes.