The studies included in this analysis were obtained by performing a comprehensive electronic literature search using Embase, Medline, Pubmed and Web of Science from 1966 to 18th of June 2008 using the Medical Subject Heading Terms (MeSH) related terms of bodyweight, waist-hip ratio (WHR), body mass index (BMI), body fat distribution, overweight, obesity, weight change, weight gain, body weight and diabetes related keywords (i.e. diabetes; diabetic; NIDDM; diabetes mellitus).The studies published by Colditz et al. [5], Carey et al. [6], Field et al. [7], and Hu et al. [8] analyzed the same dataset from Nurse's Health Study.The most recent publication from that study - that of Hu et al. - was included in the analysis.Only studies meeting the inclusion criteria of (1) analyzing the relationship between overweight/obesity and diabetes in a prospective study; with reporting of a relative risk or hazard ratio; and (2) analyzing the risk associated with overweight and obesity as categorical variables were further analyzed.Some articles sounded relevant at the title stage, however, after reading the abstract, it was clear that they did not analyze or report the relative risk of type-2 diabetes for overweight or obese people from a prospective cohort study.Combining results of these predictor variables with health outcome then produced 3585 obesity and diabetes related studies.Consequently 18 studies matched all the inclusion criteria and all relevant information was extracted for further analysis.