I've heard that if yoy haven't gotten your period by 16, you should go to the doctor and get it checked out. Some people are 10 when they get it, others are later. I was 14 and trust me. I'd rather be even later!
My cousin was 14 and hadnt had hers yet and was practically begging for it to come and I was telling her she didnt actually want it. When she finally did she was like... you were right. Periods suck. XD
So honestly, just live period free for as long as you can! XD I think weight does impact periods but I'm not 100% sure.