Start by visiting blogs in your niche, and participating in conversations. When you leave a comment on a blog, it will ask you for your name, email address, and website. In the website box, leave the URL of a hub that you have which is closely related to the blog post you are commenting on.
If you're not sure how to do this... just open up your hub-page, copy the whole http...etc from the address bar, and paste it in the appropriate box. You can use a shortening service, like bitly.com, if it is too long, and won't fit. When your comment is published, and someone clicks on your name, it will now take them to your hub.
Congratulations, you now have a backlink! :-)
You can also look for forums in your niche eg. search for 'weight loss forum'. When you join a forum, you will have the option to have a 'signature', which will appear below every comment you make. Make your signature the URL of the best hub that you have, or perhaps your hubpages profile page, so that you will impress any visitors.
As always, you are aiming for human visitors, so make sure every comment and hub that you do is quality. Do not spam, or leave short comments; it will result in all your comments and profiles being deleted eventually, and undo all of your hard work.
Social media, ie. facebook, twitter, etc, is another place to mix with like-minded people, and leave links to your content. btw, If it sounds like a lot of work - it is! :-) Instead of spending all of your time pumping out Hubs, you should aim for a couple of quality hubs per week, balanced with some subtle and ethical promotion (IMHO).
Getting backlinks for search engine rankings is (arguably) a waste of time these days. Instead, you really need to impress real people, and get them to visit your site. That is the way of the future.
Hope this helps,