A particular food cannot speed up your metabolism. Every now and again you hear of something that supposedly can e.g. lemons/grapefruits but it's not true. Missing meals slows your metabolism, excercise and cigarettes are two thing that speed it up. If pineapples could speed it up they would have discovered it hundreds of years ago and we'd all be eating them constantly before going on holiday and after Xmas!
many things are claimed to speed up the metabolic rate or break down fat, nothing has ever been properly proved .
so don't beleive what some will tell you.
eating a healthier diet with plenty of fruit and veg,if you eat smallish meals about 5 times a day this should help to speed up the metabolic rate, regardless of wether you eat pineapples or not
Don't know about metabolism, but after eating nearly a whole fresh pineapple last week, it really made the roof of my mouth sore, can't think why, except for being a greedy moo!
I can't help about the metabolism, but as jsbuttonsw says pineapple contains a powerful digestive enzyme called bromelain which prevents indigestion - a very handy fruit for a pud if you've overstuffed with the first course.