Several low competion keywords in the same niche, what to do?

I have found several (17 to be exact) low competion keywords all in the same niche (loss weight)...
Now I am asking myself if it would be better to build one large site or several MNS
with one big site I am unsure if I am able to rank. However it seems like MNS are
getting punished on a regular basis from google, but it also seems like a spread of risk. What is you oppinion?

Exact Search results for every keyword are around 50-100k with nearly no exact domains and bad backlink structure, they receive around 2000 searches each.

edit BTW I want this to be as passive as possible with me doing as little work as possible from a certain point on!

I would go with one large authority site.

i would go for one site.

I have the same thing for pets niche, I was debating what to do, and decided one big site would be best.

Yeah I would prefer one site, too. Simply because its easier but with the small ones I could use the keyword in the title and rank much easier,
that is the crucial point that I am afraid of not being able to rank...

one large authority website is your best bet

I agree with the others, make one large site. Structure it properly and target all keywords.