It can also be a negative value. If I diligently track calories using one of these things and don't lose weight I'll say "screw it" and stop bothering because

It can also be a negative value. If I diligently track calories using one of these things and don't lose weight I'll say "screw it" and stop bothering because obviously counting calories doesn't work. I think this is much more likely to be the case because even proper calorie counting is difficult and frustrating