Increased heart rate is only one of the side effects of taking certain weight loss drugs. I don't think the risk of "taxing" one's heart is the real health risk. The more dangerous side effects from long term use of most of these kinds of drugs are the ones that you can't "feel" right away such as dangerously high blood pressure or liver/kidney toxicity.

I think a lot of folks take so called "natural" weight loss herbs thinking they are safer than other kinds of over the counter or prescription weight loss meds. But they really aren't any safer. In fact for folks on other meds, herbal supplements can actually be downright dangerous.

-traveller