"Bitter orange contains an active ingredient called synephrine that is similar to ephedra.
Many weight loss and bodybuilding products contain bitter orange and caffeine, which can cause high blood pressure and increased heart rate in healthy adults. There is concern that using bitter orange might cause heart problems.

Bitter orange (synephrine) is considered a banned substance by the National Collegiate Athletic Association (NCAA).

Bitter orange has many chemicals that affect the nervous system. The concentration and effect of these chemicals can change based on the part of the plant used and how it was prepared. These chemicals can squeeze blood vessels, increase blood pressure, and cause the heart to beat faster."

Would say people mainly us synephrine for fat loss. if it works or not is another question.