I dissagree. Spaniards are couch potatoes and they are not fat. It's the diet. (Well Mediterranean diet is also dissapearing too).
Thanks God, I belong to the "old generation" of Spaniards (I'm 34) and I don't like sodas.
Well, diet is certainly a factor. If you burn 5000 calories a day and intake 10,000, the exercise wouldn't prevent weight gain.