Solos for the Weight Loss Niche?

That is exactly where I want to be with my list. It's easy to build a list with solos in the IM niche, but I feel like it lacks the relationship needed to make continuous sales and residual income, plus I think the health/fitness niche is more evergreen.....

Tal (just above) is right, of course.

This is not a niche in which the subscribers on "other people's lists" are likely to be of much value to you, Nicolas. Even if you can find them.

You need to look at it in terms of who those people are, how they got there, and what they've already received in the past, and then ask yourself why whatever the list-owner sends them "for you" is going to be significantly different from, or better than, that.

The value of email marketing comes in the form of the relationship that you build with your subscribers, the trust and respect they have for you, and the strength that your recommendation carries for them. It's all personal. That's what most email marketing is about. The theory of "solo ads" is that you can achieve a small part of that vicariously, with someone else's subscribers, when the someone else does the mailing for you. But the question you have to ask yourself is how likely that is to work productively for a third party (you), if that's the kind of thing those subscribers are used to receiving. Is the trust-based relationship with a list like that really going to be strong enough?

You've done well, in principle, by finally branching out from "MMO" to a different niche, I think. But be aware that in a niche as competitive as this, the thing that's guaranteed is that you're inevitably going to be competing for the same traffic with some of the most experienced, profitable and successful marketers there are.

The reality is that even if you get some people from the solo ad provider's list on to your own list (which ought to be the purpose, of course), they're still not likely to be very good quality leads, if you've found them this way.

You're right to be looking at email marketing, of course: there's no question about that. But the reality is that it's going to become profitable for you when you build your own list from your own traffic. And here are a few threads which explain why that is ...

Is it a good idea to spend some time on building a mailing list ?

Without Building a List, How Consistent is Your Income from Affiliate Marketing

Does anyone even make money online without an email list?

(I appreciate that you're already trying to build a list, and that that's why you've posted, but reading through many of the points explained in those three threads will help you to appreciate why solo ads may not really be an appropriate way to try to do that, in this case.)