Hey to all of you guys. There may be side effects but as an exercise professional you have to understand that this stuff has caffeine even if you drink coffee your heart beats faster its part of the pills process. You must workout, eat right and drink alot of water I am sure I hate to say most of your diets are bad no pun attended. Any weight loss supplement will give you negative side affects because they have supplements in them to help your body heat up to lose weight its just part of taking these pills. Everyone will have different side effects but I would never tell anyone if they asked me about this not to take it. I know numerous of clients that have lost extreme weight because they took it exercise correctly and ate right.