Doing a legit study is hard, and expensive, because there are a million things to control for. Finding even 30 people who live basically identical lives, and ar

Doing a legit study is hard, and expensive, because there are a million things to control for. Finding even 30 people who live basically identical lives, and are physically identical, and who are prepared to actually do something specific to themselves is a major barrier. But 30 is a bare minimum. 60 is better (ie 30 active, 30 control) and the ideal is in the thousands. Even the fact of taking money to be in a study is already non-normative, and has to be controlled for. So, take any study on human behaviour with a huge pinch of salt. That said, some studies can be replicated, and correlate well with what we experience. Dunning-kruger and loss aversion are easily (and often) replicated, but also correlate well with everyday experiences. When it comes to diet and weight-loss though, well, consider it all rubbish IMO - 99% is rubbish, and figuring out the 1% is hard.