Some of the common ways girls get fat in stories are through unhealthy eating habits like snacking constantly on junk food. Also, they might have a sedentary lifestyle, spending a lot of time sitting and not being physically active. Sometimes, certain medications or medical conditions can also cause weight gain for the girls in the stories.
To obtain stories in Girls Frontline, you could try reaching certain levels or achieving specific achievements. Also, sometimes special events offer story rewards. Keep an eye on in-game notifications for such opportunities.
I'm honored to recommend you a fat girl romance novel called Compromise, My Fat Sister. This was a modern romance novel with a health theme. It was about a fat sister who tried her best to change herself and finally won love. If you want to see the growth of the heroine and a passionate and romantic love story, this book is worth reading. I hope you like my recommendation. Muah!
There are also community sports clubs that welcome girls. They can take part in activities like basketball or swimming lessons there. Many local gyms offer programs specifically designed for girls to get into fitness and sports.
Well, it could be due to a combination of factors. You might have had an irregular eating schedule, lots of sugary drinks, and spent too much time sitting instead of being active. Stress and lack of sleep can also play a role in weight gain during high school.