I am natural, and in all honesty, the more I read about fat burners, the less keen I am on them.
There are almost always sides that could have you back where you started or even worse.
As a tool used for bodybuilding comps, they are very useful in getting ready for a show, but to maintain a lean body long term, the majority of them are highly counter-productive.
T3 is indiscriminant, it will burn both fat and muscle. Burn muscle, which women have a harder time acquiring and maintaining, you lose that lovely shape to your limbs, and your metabolic rate goes down, so when you are off the drugs, you will have to eat fewer calories than when you started.
That is why T3 is often stacked with a steroid.
Clenbuterol down-regulates beta-3 receptors quickly and often stops working within 3 weeks or you have to up the dose, but again, adaptation. Some women can't handle the sides. It also suppresses the thyroid, so that is why people often stack it with a thyroid medication (see above)
ECA stacks, ephedrine, caffeine and aspirin seem to be one of the best stacks, but it has problems as well. High levels of caffeine increase cortisol levels which will not only eat away at your muscle (cortisol causes glucose to be released into the blood stream), and also triggers insulin release. The cortisol-insulin combo is thought to result in excess belly fat.
Aspirin inhibits inflammation, which is necessary for muscle growth.
I personally think most women are better off with a sensible diet they can maintain for life, and a non-stimulatory over the counter fat burner.
There are a lot out there, but a few available from this site have gotten rave reviews.
The issue with OTC fatburners is that if you have a lot of fat to burn, they are not as effective until you have lost some fat, and the diet and training are working.