Trials claiming benefits of weight loss *actually* measure many effects of pleiotropic interventions (incl. weight loss). But we don't manipulate weight. No manipulation, no causality.

It's scientifically irresponsible to confuse a DEPENDENT VARIABLE W/ THE INDEPENDENT VARIABLE
I am a fierce advocate for exercise and healthy foods. I reject the idea that they matter only insofar as they decrease weight. But that's the message of these studies. Weight loss gets all the credit. It gets the title. It gets the abstract. It gets the punchy headline.
Let's have some fun today. Anyone on #medtwitter #nursetwitter or just a human interested in the *body weight independent* benefits of exercise and fitness on the following: NAFLD, asthma, diabetes, hypertension, all cause mortality?

or how about just improving quality of life?
The following studies show that you can be healthy and larger bodied, that fitness is a stronger predictor of healthy than body size, and that these benefits do not depend on weight loss.
Cardiorespiratory fitness predicts cardiovascular and all cause mortality in 13,155 men with hypertension followed for 12 years. Effect of fitness is independent of BMI and %body fat.
Let's review table 5--all cause and cardiovascular mortality as a function of both body size (vertical columns) and fitness (horizontal rows). Hazard ratios (HR) measure the "extra" risk compared to a defined reference group (in this case, fit people with BMI 18-25). Low HR=good
Scan the hazard ratios as you move vertically down the columns, comparing the risks of diff. body sizes (black box). See how similar they are?

Scan the hazard ratios as you move horizontally, across fitness categories (magenta box ). See how different they are? Image
This kind of effect isn't an outlier. Plenty of evidence shows the benefits of exercise which are independent of body size. Let's look at some more:
Exercise dose-dependently improves quality of life in 430 sedentary post-menopausal women. This effect is independent of weight loss.…
A 35% increase in weekly exercise improves asthma control in adults in *all weight groups* (n=44 intervention, n=45 control)…
Thorogood et al report disappointing lack of weight loss resulting from aerobic exercise alone in this meta-analysis.

Burying the lede! which shows isolated exercise improves blood pressure and lipid markers despite minimal effect on body weight.
High intensity mixed aerobic and resistance training reduces markers of inflammation in people with metabolic syndrome over 12 month period independent of weight loss

(this study does report an association with waist circumference)
Changes in cardiorespiratory fitness, *independent of BMI*, predict all cause and cardiovascular mortality in 14,345 men followed for 11 years.…
Resistance training reduces liver fat in non-alcoholic fatty liver disease *independent of weight loss* over 8 week period in 11 sedentary patients
Baseline data from Look-AHEAD clinical trial (n=5145) compared fitness and BMI. Fitness is a stronger predictor of A1C (proxy measure of avg blood sugar), ankle brachial index scores (peripheral artery health) and Framingham Scores
There should be literally hundreds more of these studies. But very, very few people analyze the impact of their interventions independent of body weight. That's too bad. Our assumptions get in the way of our science and our health.
If you can move in a way that feels good and is safe, do so. In my opinion, weight is a dangerous distraction.

I recognize the ability to exercise safely is inequitably distributed along racialized and gendered and body-sized lines. *That* structural violence harms health.

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with robert rosencrans

robert rosencrans Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @rfrosencrans

13 Sep
In #RaceInABottle, Jonathan Kahn exhaustively documented these studies. Tiny, non-random samples extrapolated to millions. Bad statistics + bad theory. I prefer a different subgroup, repeatedly shown to have biologic import: astrological sign. A thread:…
For no reason in particular, I will point out that analyses just like this have found powerful biological differences amongst people from different astrological signs. Pisces patients have a decreased risk of sepsis death following fluid restoration.
On the perils of subgroup analysis, part II:

Gemini and Libra patients do not benefit from aspirin post myocardial infarct…
Read 6 tweets
31 Aug
I’m an adipose tissue biologist. I study sympathetic nerve action on adipocytes. This month is my first committee meeting since beginning to intensely read weight bias literature. I’m nervous to hear a group of old school researchers respond to my new ideas. But it isn’t optional
It’s about responsible conduct of research. it’s also about me. I’ve never been a “normal weight”. Ever. 10 year vegan, 15 year long distance runner. I’m engaged in auto-ethnography deconstructing my own health journey. Decoupling weight and health.
These are the things I know: exercise and healthy, culturally appropriate diet are critical to human health. Large bodied and small bodied people do not consistently differ in these variables. I know this from data. I know this because I am one of these people.
Read 11 tweets
1 Aug
Much rhetoric around obesity as a critical pre-existing condition for Covid-19.

A key lesson from H1N1 epidemic: meta analyses (n=25,189) showed an odds ratio of 1.8 for fatality amongst obese people. Until they controlled for one key variable


#HAES #fatphobia #medtwitter
Smaller bodied people *systematically* received earlier antiviral treatment than larger bodied people. Controlling for this difference eliminates impact of obesity on H1N1 fatality. Obesity kills, but the critical mediator is not biology, it's bias.
H1N1 and coronavirus are not the same; but these results should encourage us to think critically about the current alarm bells. The concern should be directed inwardly, to providers, and outwardly, to an inequitable society.
Read 7 tweets
8 Jun
Friends, especially White friends, in academic medicine wondering what you can do and what issues you can advocate for. A non-comprehensive breakdown by specialty. I remind you that pledging to stop hate is not enough. What you do in this moment should make you uncomfortable.
All: Faculty should advocate for a *written* statement from their Deans stating: any med student arrested in connection with protests (for any reason, violent or nonviolent #CopsLie) will not be penalized, but will instead receive a letter of commendation for living their oath.
Medical students are one of many groups out here risking our lives. Will you risk writing an email to protect our professional futures?
Read 24 tweets
10 Apr 19
my personal rule: when a biomedical researcher starts discussing putative biological differences across the (stable, eternal, ahistorical) "races", quadruple check their citations.
unsurprisingly, they almost always fail to apply the concept of social construction (although they understand it). much more surprisingly, they are often wrong in regards to the specific findings they are describing.
today, my pharmacogenomics professor informed us confidently that "blacks have low Cyp3a5 activity". (cyp=enzyme that break down certain drugs)
Read 9 tweets
8 Dec 18
“Sickness doesn’t terrify me, and death doesn’t terrify me. What terrifies me is that you can disappear because someone’s telling the wrong story about you.”

This film gut-punch reminds us that medical research is always lost before it’s found. But progress begins with believing in patients’ experiences.
It takes an arrogance, at this stage in biological discovery, to reduce symptoms to a patient’s imagination. Our measurements are not so powerful, our theories not so complete. There is time yet for more than one paradigm shift in the biology of complex diseases.
Read 7 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!