A few examples of Sampling Bias in Fitness.

I originally posted this on Facebook, just wanted to share my thoughts. Since the post was well received, thought I’d make a post here in the website as well:


A particular bias I find very interesting is the selection bias. I think in this case it may be called sampling bias. I’m not sure, but I’m not too interested in semantics.
I’m going to give one example of it. This includes 2 people: Alan Aragon and Spencer Alan. I chose to not hide their names so the examples can be better understood as I figure most people reading this know them. This isn’t calling them out or anything of the sort, I have a huge respect for both, and they both know it.
The first example is the idea that doctors often give bad advice, usually specific to training or nutrition. This topic arrives often, and it has come up in threads containing both Alan and Spencer. When that happens, they usually clash. I’ve seen this at least 4-5 times over the years. Spencer laughs at the idea that doctors aren’t knowledgeable in nutrition. I’ve seen him argue that if that were the case, they wouldn’t be able to pass their degree (or a similar argument, can’t recall the exact details). Alan on the other hand, believes this is false on a general level, and believes most doctors are ignorant about nutrition. Of course, Alan agrees that some doctors are exceptional, but ignorance is the norm. Meanwhile, Spencer agrees that some doctors are exceptional, but argues that adequate knowledge is the norm. Who’s right? I don’t have the answer, but if you think about the background of both, their positions make more sense.
Alan is an expert on nutrition. He makes a living on educating people about the topic and debating people that spread misinformation. He has heard hundreds of situations where bad advice was given by doctors. And many of us in the field can relate. Creatine is bad for your kidneys, whey protein is harmful, fruit is bad because of sugar, carbs automatically make you fat, and countless other nonsense. However, it’s important to remember that these are the situations that stick with us because they bothers us. Who remembers the doctors who said whey protein is fine? That while carbs may be more prone to over-eating, calories still determine weight loss? Things that are normal don’t stick as well in our heads. Therefore, we subconsciously create an illusion where there is a mismatch in terms of frequency for both situations. We tend to remember the bad advice, and forget the good advice. When the doctor gave accurate information, people probably didn’t complain to Alan, and therefore those situations weren’t presented to him.
On the other hand, Spencer believes most doctors are decently knowledgeable in nutrition. Of course, he is a doctor himself, so that makes him a bit biased from the outset. But on top of that, he’s an extremely knowledgeable person that actively seeks to improve his care, is on top of the literature, talks with many experts on a frequent basis, etc. That’s not the norm for most doctors (this is a totally separate issue, the fact that they don’t obviously doesn’t mean they’re bad doctors or even that they give bad nutritional advice). Spencer frequently visits conferences, which attract people just like him: hungry for knowledge and truth, constantly trying to improve care, very aware of the literature, etc. He also frequently engages with other highly knowledgeable doctors and experts. Just like Alan, this may distort his idea of what an average doctor is, simply in the opposite direction.
Another example is the topic of obese people being “lazy” about their weight and health. Spencer absolutely despises this idea (with many good arguments on his side). But again, if you think about it, what’s the population Spencer works with? For example, every day he sees patients that come to him in his clinic. But because they come to him, that population is already partially filtered. If they were “lazy” and didn’t bother to have a positive change, they wouldn’t be in his office. He’s less likely to be aware of people who don’t try very hard to change. The people who seek for his help have likely been trying to change for years, but they simply fail every time. Despite that, they’re still there, trying to finally find a solution and improve their lives.
On the other hand, the general population might see everyone that is obese or overweight as lazy, when in fact many of them may not. We just don’t tend to see their struggle, and past experiences that agree with our biases are more memorable to us.
I’m not saying both parties aren’t aware of this, I’m sure they are. Of course, I’m biased myself writing this. Just thought it would be interesting to share.

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