Don’t fight puberty. That will just lead to issues and health complications later that are so much worse than not having that muscular, lean look. These are some of the most critical years of your life for developing bone strength. It might not seem like a big deal now and you might think the stress fractures and tendon issues won’t happen to you, but trust me, they happen.
As a fellow female athlete, I really urge you to not think about your appearance and instead focus on your training and health. Although my situation is slightly different, I was also focused on looking lean. I took it too far (it’s easy to do and so many have done it) and lost my period for three years. I ran well for a year (this is a classic example of what happens), until I got into this injury cycle. I haven’t run in two years because of it. My sleeping is coming back and so is my energy and personality (I couldn’t sleep over three hours a night and was also moody), but I made my body fragile and it’ll take awhile for it to become strong and trust me again. I finally have my period, but my body NEEDED the weight and was sending me so many signs until it finally shut down. My example might be extreme, but you’re so much more than your appearance. You’ll most likely gain a little weight during puberty and then maybe lose it in a few years as your training load (slowly and gradually) increases. There’s no way to tell, but please don’t fight it.
One of my best friends in college was a little heavier than the classic distance runner. She always ate healthy and was shocked to learn that so many on the team had irregular periods. She was the only one who never got injured. Fast forward a couple years, and now she’s the leanest of everyone. She was able to slowly build her mileage over the years and be consistent in her training. She did it in a healthy, sustainable way. She doesn’t try to be lean, she just trains hard. Still has a monthly period and everything and just broke 2:30 in the marathon last spring. And she credits so much of her success to her nutrition (mostly quantity) so that she can hammer those 100+ mile weeks month after month.
As someone else mentioned, strength training will be your friend. Keep running. Focus on how you feel and getting strong. In ten years, you’ll be so happy that you didn’t get stuck in that trap. Being strong and healthy and happy is a billion times better for your body and mind. I understand it’s hard! But you have a really bright future if you choose the healthy path now.