Niche – too narrow/specific?

Dear Brooke,
Thank you so, so much for including the Entrepreneur Course in SCS. It is amazing – you truly practice what you preach as you have overdelivered in the most wonderful way! You are awesome.
Upon your suggestion in a previous question I am trying to settle on a niche as a weight loss coach. I initially chose women with kids who want to reach their goal bodies in terms of health and weight (a group I have already been working with a bit). Now I am thinking to add the age range of ‘in their forties’. This would allow me to focus on specific issues that affect women in this age range that I am also a part of! Do you think that is too narrow? Would I be shutting out other potential customers who are younger