There are various factors, such as efficiency and cost, that people take into account when they decide what to do in order to keep their health. However, I believe the most important factor is effect, so exercise is the best way to improve health. In the following paragraphs, I will illustrate in detail why I think this way.
To begin with, exercise helps people to maintain physical health. It is very important for people to have strong immune systems in order to keep physical health because robust immune systems make people be less susceptible to illnesses, such as a cold and pneumonia, that are caused by viruses and bacteria. Considering this, exercising is a great way to keep physical health. This is due to the fact that exercise stimulates immune cells to fight more actively against viruses and bacteria so that people can have more strong immune systems. A study conducted by Tokyo University demonstrates that exercise strengthens immune systems. Researchers performed the study with 200 people of similar health status. Half of the people were required to exercise regularly, but the other half were not. After a year, researchers measured all the people's immunity levels. The result was that, in general, the people who exercised regularly had more active immune cells and higher immunity levels than those who did not.
On top of that, exercising helps people to maintain mental health. Today's people have a variety of issues, such as work, study, and personal relationships, in their lives that cause stress. Because even low-level stress can disturb their concentration and cause mental illnesses, such as depression and insomnia, proper stress management is vital for today's people in order to keep mental health. My personal experience shows this is true. I recently felt a lot of stress when I was studying for my final exam. Even during the times when I was not actually studying, I was under mental pressure. One day, I decided to take a study break and met my best friend. We played tennis for three hours. While I was exercising, I completly forgot about the exam and lost myself in the activity without suffering from stress.
To sum up, exercise has a positive effect on maintaining physical and mental health. In this regard, I firmly believe that exercising is the best way to stay heatlhy.