Why are my parents so worried for nothing?

They're worried just because I decided to eat minimal junk food because I used to eat a lot, and because I decided I wanted to lose weight I'm 5"2 and I was at like 137 and so I'm like 115-118 now and they're concerned about it because I don't eat like a pig anymore.. I still eat ike 1200 calories a day so it's not like im starving myself. How can I get them to stop worrying? I exercise a lot on my bike too.