Does fast food really shorten your life?

My mom and I were very unhealthy, meaning we went out to eat at Mcdonalds alot, but we made lots of changes. (Now we’re much healthier than before) But as i was making these bad desicions when i was younger I always heard that fast food shortens your life and kills your brain cells.

My question is Does fast food killy you a little, I know its not the healthiest food for sure but, is that true?