Table 1 Inclusion and exclusion criteria

• Only empirical research from published and grey literature that have examined modifiable risk factors with T2DM as an outcome measure will be included in this study.

• All studies published from 2000 to 16 November 2017 will be included to coincide with the Millennium Development Goals (MDG) launch. Also, since the WHO diagnostic criteria for diabetes was widely accepted from 1998 [18, 90] and revised in 1999, studies conducted earlier may have used different criteria for diabetes diagnosis [95].

• Only studies reporting quantitative data will be included. These may include cross-sectional, cohort, longitudinal and case-control studies.

• Studies will be included, if fasting blood plasma (FPG) and oral glucose tolerance test (OGTT) were measured in accordance with the WHO criteria [96].

• The most recent study from a duplicate publication of the same data will be considered.

• Only studies published in English will be included.

• Studies with impaired glucose tolerance (IGT) and impaired fasting glucose (IFG) as outcome measures will be excluded from this study.

• Risk factor definitions that do not correspond to the WHO criteria will be excluded.

• Reviews, commentaries and letters will be excluded.

• Studies that are rated as low quality in the risk of bias assessment will be excluded.