Previous studies have established a link between obesity and type-2 diabetes, and the epidemic of obesity among children, adolescents, and young adults is a major public health concern.  Joyce M. Lee, from the University of Michigan (Michigan, USA), and colleagues analyzed data collected on 8,157 adolescents and young adults, ages  14 to 21 years at the start of the National Longitudinal Survey of Youth, and followed them for an average of 15 years.  The team calculated excess body mass index BMI-years by subtracting the actual BMI from the reference BMI (25.0 for adults or 85th percentile for adolescents) for each study year and cumulating excess BMI for the study duration. The longer one has an excessive body mass index, the greater the risk of developing type 2 diabetes.  White men age 40 with 200 cumulative excess BMI-years had an almost threefold higher odds of developing diabetes than men of the same age and race with 100 excess BMI-years.  Further, for those with 200 excess BMI-years, researchers found a higher risk of developing diabetes among 30-year-olds compared with those at 35 and 40 years.  Commenting that: “A higher level of excess BMI-years was associated with an increased risk of diabetes,”  study authors that: "Because younger compared with older individuals have a higher risk of self-reported diabetes for a given level of excess BMI-years and cumulative exposure to excess BMI is increasing among younger US birth cohorts, public health interventions should target younger adults.”