四级英语作文的满分是15分，考试时间为30分钟。写作部分是大学英语四级考试中的一个重要组成部分，要求考生根据所给的主题或提纲写出一篇完整的短文。内容通常涉及社会热点问题、文化差异、教育科技等广泛的话题。文章一般需要包含引言、正文和结论三个部分，语言要流畅，逻辑清晰，表达准确。

下面提供一篇关于“健康饮食”的英语作文示例，约150词：

Title: The Importance of a Healthy Diet

In recent years, with the fast-paced lifestyle and the increasing popularity of fast food, more and more people are neglecting the importance of a healthy diet. However, a balanced diet is crucial for our health.

A healthy diet not only provides us with sufficient energy but also helps to prevent various diseases. It is necessary to consume a variety of foods, including vegetables, fruits, whole grains, and lean proteins, which can supply us with essential nutrients. In addition, a balanced diet can help us maintain a healthy weight, which reduces the risk of obesity-related diseases such as diabetes and heart disease.

To sum up, a healthy diet plays an important role in our daily life. Therefore, we should pay attention to what we eat and try to develop good eating habits. Only by doing so can we enjoy a healthier and happier life.

请注意，这只是一个示例，实际写作时应根据具体题目进行调整。希望对你有所帮助！