The study revealed more than 47% of Spaniards aged 18 to 64 are overweight or obese, while one fifth of boys aged 15 to 15 weigh above the average.
The number of girls who are overweight has increased by 100% since 1996.
Andalucia, Asturias and Galicia, have the highest obesity levels, while the Balearic Islands, Catalunya and the Basque Country are among the lowest.
The figures come from a General Directorate of Public Health study published last week.
“All people have an individual responsibility, but in our society the ability to choose a healthy diet at an affordable price is complicated,” said nutritionist Miguel Angel Royo.
Poor exercise and diets too much meat and lacking in fruit and vegetables were cited as fueling the obesity problem.