Preventing progression to type 2 diabetes

Defining risk 

Risk factors for type 2 diabetes include:³ 

• demographic and social factors – age, family history, ethnicity 
• lifestyle factors – obesity, physical inactivity, smoking 
• clinical history – high blood pressure, high triglycerides and low high-density lipoprotein cholesterol (HDL-C), gestational diabetes, heart disease, stroke, depression, polycystic ovary syndrome, acanthosis nigricans and metabolic-associated fatty liver disease (MALFD) 
• medications – including corticosteroids and antipsychotic medications. 

Clinicians should be alert to the possibility of type 2 diabetes in people with these risk factors, many of which are also risk factors for cardiovascular disease. 

The ‘metabolic syndrome’ (defined by the presence of at-risk measures for waist circumference, triglycerides, HDL-C, blood pressure and fasting glucose⁴) confers a three- to fivefold increased risk of type 2 diabetes, as well as an increased risk for cardiovascular disease.⁵ 

People with MALFD are at twice the risk of developing type 2 diabetes as the general population.⁶ 

Particular population groups are also at greater risk of developing type 2 diabetes, such as those with a high-risk ethnicity/background (Aboriginal and Torres Strait Islander, South Asian, South-East Asian, North African, Latin American, Middle Eastern, Māori or Pacific Islander people, including individuals of mixed ethnicity).⁷ (Refer to ‘Who is at risk of type 2 diabetes?’ in the section ‘Defining and diagnosing type 2 diabetes’.) 

Aboriginal and Torres Strait Islander peoples have more than three times the prevalence of type 2 diabetes than non-Indigenous Australians, with onset at an earlier age.⁸ Waist circumference has been found to be a strong predictor of the risk of developing type 2 diabetes, especially in Aboriginal women.⁹ For advice on the prevention of type 2 diabetes refer to ‘Chapter 17: Type 2 diabetes’ in the National Aboriginal Community Controlled Health Organisation (NACCHO)–Royal Australian College of General Practitioners (RACGP) National guide to a preventive health assessment for Aboriginal and Torres Strait Islander people.¹⁰ 

Other groups particularly at high risk of developing type 2 diabetes are people with IFG, IGT or gestational diabetes.^11,12 (For definitions of these states, refer to ‘Defining and diagnosing type 2 diabetes’.) 

Progression to type 2 diabetes in people at high risk 

Annually, approximately 5–10% of people at high risk develop diabetes, although this varies according to age, sex, family history and ethnic background.¹³ Three-quarters of people with IFG or IGT will develop type 2 diabetes over their lifetime.¹⁴ People with IFG or IGT whose glucose metabolism returns to normal, either as a result of interventions or spontaneously, have roughly half the risk of developing type 2 diabetes compared with those with persistently abnormal glucose metabolism.¹⁵ 

Women with a history of gestational diabetes have an approximate 7- to 10-fold¹⁶ elevated risk of future development of type 2 diabetes depending on diagnostic criteria applied to this population.^17–19 

Evidence for lifestyle interventions to prevent type 2 diabetes 

In randomised controlled trials, intensive lifestyle interventions have been shown to reduce the rates of progression to type 2 diabetes by 27–45% over periods ranging from 10 to 23 years.¹ Recent analyses suggest that longer-term (more than three years) with sustained (mixed lifestyle and medication) interventions may reduce the risks of cardiovascular disease, retinopathy and mortality in identified high-risk people across different population groups.²⁰ (Refer to ‘Who is at risk of type 2 diabetes?’ in ‘Defining and diagnosing type 2 diabetes’.) 

People at high risk of type 2 diabetes should consider lifestyle interventions to help them increase physical activity to at least 150 minutes per week, and to achieve and maintain a 7% reduction in weight if they are overweight or obese. This may involve individual or group education and coaching. Cardiovascular fitness significantly decreases the risk of progression to type 2 diabetes in people with IFG and/or IGT, whether or not they are overweight.²¹ 

In women with a history of gestational diabetes, beginning lifestyle interventions soon after pregnancy has been shown to reduce the incidence of type 2 diabetes by 25%.²² 

Other interventions 

There is evidence that, in high-risk people, metformin reduces the relative risk of developing type 2 diabetes by approximately 25%.^23,24 However, metformin is not licensed by the Therapeutic Goods Administration for this use in Australia. 

There have been no randomised controlled trials of the effect of bariatric surgery on preventing progression to type 2 diabetes. Longitudinal studies have observed longer-term reduction in progression from IGT to diabetes (ie return to nonormoglycaemia) at rates of 58% at four years after surgery, with only 5% progressing to diabetes. However, results are more promising for people diagnosed with diabetes and the incidence of diabetes remission.²⁵ (Refer to ‘Remission of type 2 diabetes’.) 

Identifying people at high risk of type 2 diabetes 

Identifying risk factors for type 2 diabetes in people is a routine part of general practice. The RACGP’s Guidelines for preventive activities in general practice (10th edition) recommend assessing body mass index, waist circumference, diet and physical activity in adults every two years. Screening for diabetes risk with the Australian type 2 diabetes risk assessment tool (AUSDRISK) is recommended in all adults aged ≥40 years every three years.⁷ 

For information about assessing diabetes risk and screening recommendations for diabetes, IFG and IGT, refer to ‘Defining and diagnosing type 2 diabetes’. 

Interventions to manage diabetes risk 

People at high risk of type 2 diabetes are also at increased risk of cardiovascular disease. Thus, their cardiovascular risk should be assessed, and lifestyle change and medications considered where appropriate.²⁶ (Refer to ‘Type 2 diabetes and cardiovascular risk’.) 

Particular lifestyle interventions have been shown to reduce the risk of type 2 diabetes in people with IGT, but not in those with IFG alone. These interventions are of moderate intensity (eg at least 16 one- to two-hour sessions focusing on diet and physical activity delivered over six months by a range of health professionals). People should consider at least 150 minutes per week of physical activity²⁷ and a low-glycaemic index diet rich in fruit, vegetables and fibre, and low in meat and fat. 

Maintaining lifestyle change, especially weight loss, in high-risk people can be difficult. Technology-assisted modalities, including ‘apps’ that support change in diet and physical activity, activity trackers and websites providing information and referral options, are promising tools to help people maintain physical activity and weight loss.²⁸ 

Intensive lifestyle intervention may be beyond the scope of the brief interventions routinely delivered in general practice or practice nurse consultations, or even by those delivered through allied health visits as part of a care plan. People may therefore benefit from referral to a diabetes prevention program. A list of state-based diabetes prevention programs can be found on the Diabetes Australia website. 

Telephone coaching programs run by state and territory governments and health insurance funds have also shown promising results.²⁹ 

Refer to the RACGP’s Smoking, nutrition, alcohol, physical activity (SNAP) guide designed to assist GPs and practice staff (the general practice team) to work with patients on the lifestyle risk factors of SNAP. 

The Australian National Diabetes Strategy 2021–2023 includes information on reducing modifiable risk factors and areas for action to prevent people developing type 2 diabetes (pp 14–15).