I think they are referring to green coffee diet pills. We had loads of people asking about this when it first was featured on some daytime talk show a couple of years back. Best weight loss is done through a proper diet and exercise.
White coffee isn't very common and lots of people ask about it. Since you're a former barista and you plan to open your own cafe, you may want to do some research about the different levels of roasted coffee.
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Please take a look at this website. It should help answer your question: