Fat Loss Tips.

Courtene:

Ashtanga is great, like the above answer says. However, I find a traditional ashtanga practice to be too rigid – it’s the exact same poses every class, and much of the primary series (which will be the focus of most ashtanga classes you get at gyms, studios, etc.) is a seated sequence that I find rather monotonous. In most ashtanga classes, each posture is held for 5 breaths.
I prefer a vinyasa flow style or “power yoga” class (which has roots in ashtanga, but is not as rigid – its sequencing is pretty much up to the instructor). In terms of strength and fitness, Bikram Yoga is great for cardio/strength – it is a fixed sequence of 26 postures done in a room heated to 90-something degrees. You will likely either love Bikram or hate it – if you try it, be sure to hydrate well in the 24 hours before you go, and bring a lot of water and a large towel (or 2) – you sweat a LOT (I’m not a fan of this form of yoga, for a couple of reasons, one being that I get so dehydrated afterwards no matter how much water I drink that I get pounding headaches; also I find it hard to hold some of the postures when I am literally soaked from head to toe). The purpose of heating the room to such a degree is that your muscles are more pliable as they heat up, and you can more easily get into postures.
Other types I find physically challenging – Jivamukti, Iyengar (can be a slower flow, but is challenging because you hold the poses for longer and really focus on alignment), Forrest (each pose is held for a really long time) and Taoist (I had a great Taoist teacher who moved away – most studios don’t offer this style, it’s not really mainstream in my experience).
Types that you may want to stay away from (more spiritual and/or restorative than physical) – Kundalini, Kripalu, Svaroopa. Hatha classes can be harder, or more geared towards beginners – it really depends on the instructor.
Good luck – I’ve been practicing yoga for about 4 years, and it is one of the best things I ever started doing. If I can help with class/studio recommendations in your area, let me know!