以下是一个适合四年级学生阅读的英语小故事，讲述了健康的重要性：

Title: The Importance of Being Healthy

Once upon a time, there was a little girl named Sarah. Sarah loved eating junk food and never liked to exercise. She would spend all day watching TV and playing video games.

One day, Sarah fell sick and had to be taken to the hospital. The doctor told her that her unhealthy lifestyle was the cause of her illness. Sarah was very sad because she realized that she had not been taking care of herself.

After she got better, Sarah decided to make some changes in her life. She started eating more fruits and vegetables and less junk food. She also started going outside and playing sports with her friends.

Over time, Sarah became healthier and happier. She realized that being healthy is very important and that it's never too late to make positive changes in your life.

From that day on, Sarah made a promise to herself to always take care of her body and mind. And she lived happily ever after.

通过这个故事，孩子们可以了解到保持身体健康的重要性，以及如何通过健康的饮食和运动来保持健康。同时，这个故事也可以激励孩子们主动关注自己的身体健康，积极采取行动，让自己变得更加健康和快乐。