Question: What's the difference between effectiveness and efficacy?
Answer: Effective means people who take it lose weight. Efficacious means that people who take it lose MORE weight than people who take a placebo (fake medicine).
Question: You mean that fake medicines can be effective for weight loss?
Answer: Yes, just like fake pain-relievers can reduce pain. This is what we call the "placebo" effect and it is a result of the human mind's ability to trick itself when it thinks that something is effective. This is why, for example, so many people believe that hCG helps them lose weight. They believe that it does, so it does.
Question: But real drugs work better than fake drugs?
Answer: That's right. That difference (between the effect of real and fake drugs) is what we call "efficacy".
Question: Can you give an example of where a real drug works better than a fake one?
Answer: I can give you thousands of examples but here is a really concrete one: antibiotics. If you're dying of pneumococcal pneumonia (bacterial pneumonia), an appropriate antibiotic will save your life. A fake drug won't. You'll die. The bacteria that are killing you don't care what you "believe" is effective, but they die if exposed to the right antibiotics.
Question: Alright, but weight loss isn't exactly life and death.
Answer: Isn't it? I beg to differ. But that's another subject.
Question: OK, let's move on. How can we actually tell if a drug works better than a fake drug?
Answer: By comparing the effects very carefully.
Answer: The archetypal technique is what we call a "placebo-controlled study." This involves enrolling a large number of people into a study, randomly assigning those people into two groups, and giving one group a real drug and giving the other group a fake drug.
Question: But wouldn't the people taking the fake drug lose less weight simply because they KNOW they are taking something that can't work?
Answer: Yes. I described a "placebo-controlled" study and they don't help much. What we really need is a "double-blind" AND "placebo-controlled" study. In other words, a "double blind placebo controlled study."
Question: And "double blind" means what?
Answer: it means that the participants in the study (the patients) AND the doctors and scientists running the study are all "blind" to the nature of the treatment. Nobody knows who is getting the real or the fake drugs. This is how we eliminate the bias that would otherwise occur as a result of people (or doctors) knowing who was getting what.
Question: Do double blind placebo controlled studies really work?
Answer: It depends on a lot of factors: how many people are enrolled, how long and above all on whether the placebo is indistinguishable from the real drug. If people can tell the difference between a placebo and a real drug, if the real drug produces some perceptible side effect like, say, nausea, then patients can quickly figure out what they're taking and the "blinding" fails. So, of course, it's not all that easy to really tell what really works. It is easier to tell what does NOT work since it's hard to imagine how someone taking a really efficacious drug could fool himself into thinking that it was sham in such a way as to destroy the drug's effect.
Question: Alright, so this is technical stuff, but what's the bottom line here doctor?
Answer: the bottom line is simple: don't believe everything you feel or "see". Our senses and our prejudices mislead us.
Question: I think that a lot of people would object to that. Most people seem to want to trust their guts.
Answer: That's true, but frankly it's not the way of science. Human beings trusted their guts through most of our history and look where it led us: religious wars, witch burning, racial prejudice... I could go on and on. But then about six hundred years ago this amazing idea slowly crept into our collective consciousness and that idea informed us that maybe we could actually test the world in a way that would allow us to learn answers. That is to say we devised the notion of experiment, of designing clever little ways of probing nature for answers, answers that are the same no matter who does the experiment, no matter where or when it's done. And of course as soon as we started doing this we started to learn that the world is totally different than our guts tell us and that if we want to have any chance of actually understanding what is out "There", we have to abandon our cherished beliefs, scrap the whole lot of them, and start over. That's why we have antibiotics and jet planes and nuclear weapons and electric power and television and the internet and even things as awful as "The Biggest Loser". Science works because it allows us to put our gut feelings and beliefs aside and learn the truth. That's science and that's medicine and I'm a believer.
Question: It's interesting that you use the word "believer". You could almost be describing a religious convert.
Answer: The religion of science eh? Sure there are articles of faith that underlie science. I'll admit that. But the faith is in logic and causality. Are those human constructs too? Newton would have argued them universal, Einstein too, but Bohr and Everett stood on less certain ground. Philosophy is a "hobby" of mine, but we are getting far adrift from the subject of drug efficacy. Or are we?
Question: My head hurts. I need to stop.
Answer Mine too.