Hi 'SlimDownShapeUp',
What I was getting at is if you are having trouble drawing enough visitors to your existing site - why now give yourself the task of trying to draw enough to two different sites? You could always put a blog on your existing site if you think readers are likely to engage with it (offering their comments etc).
From the
SEO perspective, yes it is certainly true that having links to your site from other sites helps your main site BUT how much it helps really depends on how 'powerful' those link sources are and a poorly read blog at Blogger, Wordpress.com or wherever is simply not going to have the 'juice' to make any appreciable contribution.
If on the other hand you have the means of promoting an offsite blog separately (and in addition) to your main site then you could maybe get a bit of a funnel effect going but you need to be quite committed to get those types of funnels working well and usually need several additional properties to post on to really make that approach work.
What are the most powerful links to a site? Well if you are trying to rank for 'slimming workouts' the best links to get would be from sites already ranking for that keyword - and their anchor text for the link to your site would be the keyword! That's a tough ask, too impractical for many link seekers!
On the other hand if you can get enough links from other health related sites and blogs, maybe get a link from a news or educational site too, you are well on the way.
See if you can write articles on other health blogs as a guest poster - in return for a link to your own site of course! In-content links from related blogs are excellent links to get
Questions about a blog 
