Could more exercise have a negative effect?

jogglesngoggles

So I'm getting very close to my goal weight so the weight is coming off at a snails pace. I'm eating at my calories and exercising. I was thinking about adding 30 minutes of running in the morning to my day to maybe speed the process along, but my sister mentioned that you can actually have the opposite effect if you do too much. Is this true? I know it's going to be a slow process, it's been 17 months so far, but I'm sooo close and want to be at my goal!