Background and objective: The prevalence of obesity and diabetes mellitus (DM) has increased worldwide. Our objective was to examine trends in the prevalence of overweight, obesity, morbid obesity and DM in Spain from 1987 to 2012. Participants and methods: Data were obtained from 8 waves of the national health surveys which are cross-sectional studies conducted in representative samples of the Spanish adult population. Self-reported data of 156,440 adults (>= 16 years) from 1987 to 2012 were used. Body mass index (BMI) was calculated from self-reported weight and height. Overweight was defined as a BMI of 25.0 to 29.9 kg/m(2), obesity as a BMI >= 30 kg/m(2) and morbid obesity as a BMI >= 40 kg/m(2). DM was considered present if the participant reported having been diagnosed. Age-adjusted prevalence was adjusted by the direct standardisation method to the 2003 survey population. Results: From 1987 to 2012 age-adjusted prevalence of overweight increased from 34.0% (95% confidence interval [95% CI] 33.2-34.8) to 35.8% (95% CI 35.0-36.6), prevalence of obesity from 8.0% (95% CI 7.5-8.5) to 16.5% (95% CI 15.7-17.1%) and DM prevalence from 4.2% (95% CI 3.9-4.5) to 7.1% (95% CI 6.7-7.4%). Morbid obesity increased from 0.20% (95% Cl 0.13-0.27) in 1993 to 0.88% (95% CI 0.70-1.05) in 2012. The growth rate was greater among males. Conclusions: An increasing trend of the prevalence of overweight, obesity, morbid obesity and DM was found in Spain from 1987 to 2012, particularly in males. (C) 2016 Elsevier Espana, S.L.U. All rights reserved.