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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
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?
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. https://pubmed.ncbi.nlm.nih.gov/19617881/
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?
Scan the hazard ratios as you move horizontally, across fitness categories (magenta box ). See how different they are?
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. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2745102/
A 35% increase in weekly exercise improves asthma control in adults in *all weight groups* (n=44 intervention, n=45 control) https://www.nature.com/articles/s41598-019-48484-8
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. https://pubmed.ncbi.nlm.nih.gov/21787904/
Burying the lede! which shows isolated exercise improves blood pressure and lipid markers despite minimal effect on body weight. https://pubmed.ncbi.nlm.nih.gov/21787904/
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) https://pubmed.ncbi.nlm.nih.gov/19695853/
(this study does report an association with waist circumference) https://pubmed.ncbi.nlm.nih.gov/19695853/
Changes in cardiorespiratory fitness, *independent of BMI*, predict all cause and cardiovascular mortality in 14,345 men followed for 11 years.
https://www.ahajournals.org/doi/epub/10.1161/CIRCULATIONAHA.111.038422
https://www.ahajournals.org/doi/epub/10.1161/CIRCULATIONAHA.111.038422
Resistance training reduces liver fat in non-alcoholic fatty liver disease *independent of weight loss* over 8 week period in 11 sedentary patients https://pubmed.ncbi.nlm.nih.gov/21708823/
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 https://pubmed.ncbi.nlm.nih.gov/18046181/
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.
I recognize the ability to exercise safely is inequitably distributed along racialized and gendered and body-sized lines. *That* structural violence harms health.
