Thread by @haileybanack

THE OBESITY PARADOX IS NOT A PARADOX

A tweetstorm by a frustrated epidemiologist

I was disappointed to see an "obesity paradox" article in @AmJEpi

Instead writing a letter to the editor, I decided that Twitter is a better way to reach ppl on #epitwitter #medtwitter

1/

Before I begin: I have the utmost respect for @easchisterman and the @AmJEpi team. But, I have a particularly strong reaction to articles claiming to have evidence of a “true” obesity paradox.

Science moves forward through scholarly debate. Let’s keep the discussion courteous!

Also, PLEASE RT and share with colleagues on #epitwitter #medtwitter #statstwitter #academictwitter

I'd love to engage and answer any questions you may have!

Here's the article I'm tweeting about:
ncbi.nlm.nih.gov/pubmed/31504124

SO. A paradox is something unexplained.

There’s this idea out there about the “obesity paradox”: obese individuals with chronic disease have a survival ADVANTAGE relative to non-obese individuals.

This runs counter to what we know about obesity in the general population.

There are several plausible methodological explanations for the "obesity paradox" that are NOT mentioned in the @AmJEpi article.

Options discussed by @MariaGlymour @_MiguelHernan @ER_Mayeda @WhitneyEpi @MatthewSperrin:
-Collider bias
-Effect modification
-Heterogeneity bias

Further, the authors cite these results as evidence of a "paradox" in ppl w/ COPD. Hazard ratios (95% CI) compared to normal weight:

Ever-smokers:
overweight=0.56 (0.43, 0.74)
obese= 0.66 (0.48, 0.92)

Never-smokers:
overweight= 1.41 (0.66, 3.03)
obese= 1.29 (0.48, 3.48)

These results are used to support the idea that an "obesity paradox is absent in never smokers with COPD"

But... you CANNOT make that conclusion from these results!!

The confidence intervals for overweight (0.66, 3.03) and obese (0.48, 3.48) never-smokers are entirely consistent with a strong protective effect OR a strong harmful effect.

AND, they overlap with the strata of ever smokers that they are apparently different from.

In conclusion, to quote @AnnaPeetersAus: "Journals should no longer accept 'obesity paradox' articles"

Given that there are compelling methodological explanations for the "obesity paradox" it is simply not correct to call it a "paradox".

Finally (last tweet, I promise):
A question to ponder for clinicians on #medtwitter:
If you believe in the "obesity paradox", you should be advising your patients with chronic disease to GAIN weight? Right? Because obese individuals have a survival advantage?

-the end-

p.s. If you're interested in learning about paradoxes check out this article Hernández-Díaz, @eschisterman1 & @_MiguelHernan on the so-called birthweight paradox (PMID: 16931543).

Q: Should we be advising pregnant women to smoke to avoid low birth-weight babies? A: NO.