Does taking stimulant laxatives (like dulcolax pills) when not needed cause less calorie absorption from what you eat since it passes thru faster?

OMG! I'm sorry, but you're mistaken/misguided. If you're often using stimulant laxatives, I assume you feel very constipated, are attempting weight loss, or are looking to "cleanse." Please reconsider & check out numerous healthtap answers that point to problems with colon cleansers & irritant laxatives, particularly when used casually & frequently. Save your health, and stop please!
Nope. the action is entirely past the point where the food is absorbed. at most changes water absorption only. AND there are many complications from cathartic use startign with the gut will become dependent on them and only move when they are taken and stop up otherwise.