Thursday, 3 January 2019

Three Easy Ways to Know If A Diet Study Sucks

LiesOne of the most frustrating things about weight loss (so-called) research, is that the media often covers any weight-loss study as if the conclusions they claim have been proven beyond a shadow of a doubt when, in fact, much of the research is embarrassingly poor – often for profit by the weight loss industry. I get a lot of questions about how to evaluate studies, and it’s a topic that can get complicated fast, but here are some easy ways to evaluate a study about a purported weight loss technique

1. Did they take their time?

This is covered in greater detail here, but basically almost everyone can lose weight short term, but almost everyone gains it back within five years. So if a study doesn’t follow subjects for at least 5 years then it’s not a valid look at whether a weight loss method works for anything more than the short term.  (This is especially important with diet companies like Noom which both claims to be a “brand new” way to diet, and simultaneously claims that they offer “permanent” weight loss. Where are they getting their long-term data? If they are “brand new,” how many people who lost weight on their program could have died having kept it off?

2. Are these people?

When it comes to the study subjects, you might think that you should start with questions like “were the study participants diverse?” But you actually need to start with the question “were the study participants human?”

I can’t even count how many times that I’ve read an article about a study and asked myself “Wait – was this rats?” and then looked it up to find that it was, in fact, done with rats as subjects. And the reporter didn’t bother to mention that while droning on about how effective this new diet is.

3. Who are these people?

If the researchers did study humans, we then have to ask how representative the sample  (the group of people who participated in the study) is. Which is to say that who they study determines to whom the study results can be appropriately extrapolated. So if they only studied white cisgender dudes, that’s the only group we can expect the results to apply to (and that’s only if they had a large enough sample – included enough white cisgender dudes – to rule out individual differences.)

A number of assumptions in medicine that have been proven false (like the idea that heart attacks have the same symptoms regardless of gender) were based on researchers’ habit of studying 150-pound cisgender white men and then extrapolating those results to literally everyone. Many studies (not just weight loss, but all studies) under-represent People of Color and completely fail to represent Trans and Non-Binary people at all. Representative samples are a huge issue, and that’s not even getting into the variables they don’t control for. So you are looking for a study with a large, diverse sample.

To date, there is not a single study where more than a tiny fraction of people were able to maintain significant weight loss long-term, so don’t be suprised if you find the weight loss studies you are analyzing are lacking in study methodology, and subject success.

If you are interested in checking out an exhaustively researched paper supporting a departure from diet culture, I recommend you head over here.

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