Is anti-hair loss shampoo really effective?

I am not currently experiencing hair loss. However, given my age and the noticeable thinning of my hair, I want to do something to prevent it in advance. I think the easiest thing to do is to use anti-hair loss shampoo.

So, for the past two or three months, I have been buying and using anti-hair loss shampoo sold in stores. What I am wondering is whether anti-hair loss shampoo is really effective.

The advertisements say it's good, but since I don't feel like anything has been actually proven or felt, I want to know if anti-hair loss shampoos are really effective or if they just serve the purpose of providing nutrition to the scalp.

Is anti-hair loss shampoo really effective?