Context

Type 2 diabetes mellitus (T2DM) is a significant and growing medical problem affecting close to 400 million people worldwide1 and almost 10% of the US population2 while imposing a major financial burden on society.3 Furthermore, an estimated 37% of the US adult population is at risk of T2DM, making primary prevention of T2DM a critical public health objective. Large clinical trials have shown that combined diet and physical activity promotion programmes are efficacious in reducing T2DM incidence.4–6 This systematic review to assess the effectiveness of diet and physical activity promotion programmes was used by the Community Preventive Services Task Force (CPSTF) to guide its recommendations for diabetes prevention and to identify gaps in research.

Findings

Fifty-three studies met the inclusion criteria and described 66 programmes. Compared to usual care, combined diet and physical activity promotion programmes were associated with significant reductions in T2DM incidence (RR=0.59, CI 0.51 to 0.66), body weight (−2.2%, CI −2.9% to −1.4%), fasting blood glucose level (−0.12 mmol/L, CI −0.20 to −0.05 mmol/L) and improved other cardiometabolic health factors including systolic blood pressure (−1.6 mm Hg, CI 2.7 to −0.5 mm Hg), diastolic blood pressure (−1.6 mm Hg, CI −2.5 to −0.8 mm Hg) and total cholesterol (−0.05 mmol/L, −0.12 to −0.002 mmol/L), low-density lipoprotein cholesterol (−0.09 mmol/L, CI −0.17 to −0.01 mmol/L), high-density lipoprotein cholesterol (0.03 mmol/L, CI 0.02 to 0.05 mmol/L) and triglyceride levels (−0.07 mmol/L, CI −0.14 to −0.02 mmol/L). More intensive programmes were more effective.

Commentary

This systematic review, conducted on behalf of the CPSTF, concludes that combined diet and physical activity promotion programmes implemented by trained providers (eg, nutritionists, diabetes educators, exercise counsellors, physicians, nurses and others) using a combination of counselling, coaching and extended support provided as part of multiple teaching sessions, are highly effective at decreasing diabetes incidence and improving important cardiometabolic health factors. It highlights the importance of reaching an intervention ‘dose’ that makes higher intensive programmes more effective than less intensive programmes (based on features such as number of sessions, duration of programme, personnel deployed and individual session format). To do so, clinicians need to consider structured lifestyle programmes as opposed to merely referring to diet and physical activity programmes, an important distinction that separates highly effective programmes from less successful ones.

The review notes the difficulty in discerning specific programme features that are most important for the outcomes studied. In addition, it does not address the relative effectiveness of specific programmes in different populations, the effectiveness of various modes of intervention (in-person, phone based, web based, etc) or the challenges related to engagement and attrition of eligible programme candidates.

Implications for practice

This study provides evidence for clinicians to consider referral of patients at high risk of T2DM into structured community-based programmes designed to provide a threshold dose of diet and physical activity programming to reduce risk of T2DM diagnosis and improvement of cardiometabolic health. Successful efforts to do so will require efficient processes for diagnosis of high-risk prediabetes, referral systems to clearly defined and accredited programmes and coverage of the costs of these services.