The main causes are a sedentary lifestyle and Spain's ageing population, said the national stats institute (INE).
The Mediterranean diet may have come to symbolize healthy eating and living, but recent figures suggest Spaniards have been piling on the kilos for the past 25 years.
INE's study, which was based on questionnaires filled out in 21,000 Spanish households, shows a 14 percent rise in the number of overweight people in Spain since the 40 percent figure of 1987.
Even more worrying is the fact that 18 percent of Spanish men and 16 percent of women are now obese.
The upsurge in chronic illnesses has been directly linked to this trend by Health Secretary General Pilar Farjas, who suggested hypertension, diabetes, high cholesterol and even blindness are heavily influences by obesity.
Farjas told El País she is convinced the negative results are not due to poor diet, but are more likely caused by an increase in sedentary lifestyles, with 14.4 percent of men and 17 percent of women declaring they don't do any physical exercise.
According to Josep Basora, president of the Spanish Family and Community Medicine Association (SEMFYC) fears the figures could be even worse: "We all tend to add a few centimetres here and drop a few kilos there when we're asked."
In other news that seems to defy the stats, organic group Ecovalia said sales of organic food went up 7 percent in Spain last year.
That makes Spain the seventh biggest consumer of organic produce in Europe, said the group.