"Some activists believe that the mismatch between Spain's clock time and solar time contributes to the country's unusual daily schedule.[9] They believe that the relatively late sunrises and sunsets shift the average Spaniard's day later than it otherwise would be, and that a return to its original time zone would help boost productivity and bring family and work rhythms into better balance.[10]" https://en.m.wikipedia.org/wiki/Time_in_Spain#Criticism_of_t...
But both Portugal and Spain are living in the wrong time zone, which is at least one hour off compared to natural solar time. So it most probably don't make a difference health wise if you move from Portugal to Spain.
Certainly, it's a plausible theory that Spain being so far off its "natural" solar time (because Franco supposedly switched timezone in WWII to be in sync with Germany) leads to the late dinners--and one I've often heard. I suppose you'd have to look into pre-WWII Spanish dining habits. Whether it's a good or bad thing? <shrug> Personally, I like lighter evenings more than mornings.
But both Portugal and Spain are living in the wrong time zone, which is at least one hour off compared to natural solar time. So it most probably don't make a difference health wise if you move from Portugal to Spain.