Compare it to a medical procedure, some things you need a professional for.
True, I would say the key factor is the severity of the issue.
If you are 10 pounds overweight, you can probably lose it all by yourself by reading up on better diet choices and improving (or starting) your own exercise routine.
If you are 50 pounds overweight, you should probably seek foundational advice from a professional nutrition and/or trainer but you may well be able to manage the weight loss process yourself with periodic check-ins.
If you are 250 pounds overweight you probably need weekly sessions with a personal trainer and a weight management programme to achieve your goals. Depending on the progress you can make, you may need surgery.
So the first question to ask yourself is: what sort of problems is this issue causing, realistically?
Is it mainly a surface-level concern, not affecting your life all that much day-to-day but you believe you would feel better in yourself if you changed it?
Is it an ongoing issue that has effects on your day-to-day ability to live comfortably/happily and work towards your goals, with the potential to cause serious long-term issues?
Or is it deeply rooted, causing considerable issues in your day-to-day life, with the potential to cause a genuine crisis?