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Chris Hu on 28 October 2025
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SvennoJ said:
shavenferret said:

Ok, and we are seeing a reverse flynn effect now.  I can link articles and academic journal studies if you like.  The point is that as america gets fatter and fatter we are losing the edge that got us to this point.  

Here is a sampling:  

1. https://www.popularmechanics.com/science/a43469569/american-iq-scores-decline-reverse-flynn-effect/     This discusses the reverse flynn effect, and notes a decline in things like verbal fluency as well as abstract reasoning because we've replaced things like philosophy with coding for better or worse. 

2.  https://news.harvard.edu/gazette/story/2025/10/researchers-report-astounding-obesity-surge-in-u-s/          This is the biggest reason as to why we are seeing a reverse flynn effect.   When the bodily machine isn't running as well, the mind won't run as well as it can.   

3.  https://www.nature.com/articles/s44220-025-00396-5   Effect of obesity on cognition...... basically echoes what i've been saying. 

The recent decline is blamed on the smart phone and worsening education, nothing to do with leaded gasoline.

The surge in obesity is thanks to the sugar lobby

https://www.npr.org/sections/thetwo-way/2016/09/13/493739074/50-years-ago-sugar-industry-quietly-paid-scientists-to-point-blame-at-fat
https://www.cpreview.org/articles/2024/6/sugarcoating-the-truth-the-role-of-lobbying-in-americas-obesity-epidemic



https://pmc.ncbi.nlm.nih.gov/articles/PMC4822166/


And labels are still misleading. recommended daily sugar is 50 grams yet in Canada the %dv indicates 100 grams daily, in the US 300 grams daily!



USA 42g = 14% -> 100% = 300 grams
Canada 39g = 39% -> 100% = 100 grams

The US version uses high-fructose corn syrup (HFCS), Canadian Classic Coca-Cola uses a mixture of sugars, including cane sugar.

The powerful corn lobby is behind the surge in obesity.



Your link for nature doesn't work, however decline in cognition (at later age) is not the same as global decline in IQ

https://pmc.ncbi.nlm.nih.gov/articles/PMC4237034/

It is abundantly evident that there is a deleterious effect of obesity/high fat feeding on cognitive performance. In human clinical studies, obesity has been shown to increase the risk of the development of mild cognitive impairment, in the form of short-term memory and executive function deficits, as well as dementia and Alzheimer's disease.

The exact mechanisms or mediators that underlie the connections between obesity and the risk of cognitive impairment are still unknown but potential avenues of further research include brain atrophy, disruption in cerebrovascular function, development of Alzheimer's disease related pathology, BBB breakdown, and systemic and central inflammation.


Dementia is indeed also on the rise, but that's more related to old age, people getting older. However obesity can also contribute to 'brain aging'. 


However smart phone / education are responsible for decline in global IQ (reading and math scores going down since 2008)
Rise in obesity is thanks to our diet, cheap sugars, processed food, leading to a decline in cognition at later age.



In the US nutrition label sugars count as carbs that can of Coca Cola gives you 14% of your daily carbs but over 80% of your daily sugar intake.  Also, that is an older label.  The new label list the percentage of total carbohydrates, directly under it now lists total sugars which includes added sugars and the daily percentage of sugars.  Anyway, the high obesity rate in the US is caused by numerous factors not just bad diets.  Other factors are low exercise rates, hot climate especially in the deep south and in most parts of Arizona which contributes to poor diets and lack of exercise by the population in those areas and cities that are designed around cars instead of pedestrians and bicycles.