i don't get why some studies have so few partipants. How hard is it to recruit people for something like this? We're not talking rare diseases.
This study did the former:
> The duration of the study is 7 days including 3 days with controlled diet and 4 days (including 5 nights) in a metabolic chamber at the Institute of Nutritional Medicine at the University of Hohenheim.
I imagine it was prohibitively expensive to have more participants.
https://www.surveymonkey.com/mp/sample-size-calculator/
If you are ok with a 25% margin of error and a 95% confidence level, 16 people is good enough. You have to make sure there isn’t some skew in your population, but if your method of sampling the population produces a skew, adding people won’t really help there.
Frequently they don’t manage to make it past the first couple levels because the results aren’t interesting.
There is a real benefit in having fewer pieces of junk to sort out and so many of these medical research studies are just noise that well meaning members of the public cite and adopt into practice because they don't know any better.
It's the modern day version of leeches, essentially.
Is part of "well meaning members of the public" just as "YouTube commentary" is and "random celebrity that Googles something and repeats it on Twitter."
And quite frankly, so are scientists themselves. I have met far, FAR too many scientists that do not know the very first thing about statistics and yet feel competent to reference other people's research.
This is why I say it's a big pile of leeches for more than half this stuff. Sure the incentives are misaligned, sure its reporting, sure this and that. But what we really need here are people to say "no you idiot leeches don't do dittly squat to fix this problem."