I agree with your opinion. The topic of health is always relevant. Many people nowadays are interested in healthy eating, health care. I would love to read such a blog.
Blogging is a good idea but if you have no idea what is your topic it's useless. Find yourself and know what is your expertise. Gaming, traveling, stock even if you are a food knowledge. You can start on any topic which you can handle with your experties.
I share your opinion, and I also don't understand why people try to follow trends without having any other motivation. They don't realize that this endeavor is doomed to failure.