My friend has been on a diet for a few weeks now.She works out every day at least an hour.She eats low fat low cal,healthy fats,all what you're suppose to do.She has lost some weight,but she takes 400mg of caffine tablets before a workout because it's suppose to boost your energy and get a harder workout.Recently I heard that the caffine pills can hinder your weight loss because it constricts fat cells? Does anyone know if this is true or what?