And interestingly, from personal experience, Spaniards are not a generally overweight population despite eating a late dinner plus a typical breakfast, lunch and even merienda (afternoon snack). What gives?
I guess this thread discusses 2nd order effects. The most important factors are still the food you eat (Mediterranean diet in this case) and the number of calories (portion sizes).
Mostly the calories. Number of meals is a non sequitur, especially with the insane caloric density of the typical American meal.