This tweet went hugely viral, as many can relate:
Sorry but how tf do construction workers get so fat that looks like a hard job idk
— Mariè (@p8stie) July 24, 2024
What is the deal with overweight blue-collar workers especially in construction, compared to sedentary office workers, who are comparably more slim? I am sure many have observed this in real life, hence why the tweet went so viral.
Like with many other things in life in which individual outcomes vary greatly, biological factors can shed some clues. Construction workers generally have 15-30+ point lower IQs compared to tech workers (85-105 vs >115). This is shown by studies of IQ versus occupation. Blacks and Hispanics, who are overrepresented in low-skilled jobs, typically have 5-15 fewer IQ points than White or Asian norms, and possibly a genetic propensity to store abdominal fat.
I have hypothesized (“Blaming Obesity on Low IQs“) that less intelligent people are more metabolically efficient, possibly leading to a propensity to gain weight despite also having jobs that entail more physical activity. Junk food is often blamed, but many office workers also eat lots of junk food and large meals, as I have observed on social media, but without becoming too overweight or obese.
The largest of Silicon Valley tech companies are known for large spreads of cafeteria food and snacks galore, all at no cost to employees. One of the major perks of working at a tech company is the food, compared to the austere conditions of blue-collar work. Again, this is just a hypothesis. It would be interesting to establish a link between IQ vs metabolism (such as REE–resting energy expenditure), but such studies do not exist.
I have observed on Twitter and other social media that smarter people seem to have an easier time losing weight or getting lean in the context of fitness or aesthetics ( e.g. bodybuilding), and this is corroborated by self-reported calorie counts when dieting. People who are smarter (using proxies such as self-reported standardized test scores and careers), are able to get lean on higher calorie counts, controlling for body composition, height, and weight.
Hispanics and Blacks, mentioned above, seem to really struggle at this compared to smarter Whites and Asians. This is consistent with the suspicion that less intelligent people are predisposed to fat storage, possibly due to metabolic differences and not just lifestyle (although this doesn’t help either). Studies have also shown that blacks have much slower metabolisms compared to whites, possibly due to the internal organs being smaller and more efficient when controlling for overall body size and body composition.
Objective: To assess differences in energy expenditure by race and ethnicity using nationally representative data. Results: We confirmed that Blacks exhibit lower resting energy expenditure than Whites—a difference of approximately 150 to 300 fewer kilocalories per day.
150 to 300 fewer kilocalories per day is huge, or about a single standard deviation of RMR. This again is similar to black-white IQ differences, of around 15 points or a single standard deviation.
At the far-left extreme of the IQ bell curve, this is also corroborated by studies, although metabolic factors are not implicated:
Studies on borderline intellectual functioning (BIF), defined as an IQ in the 71–84 range, indicate that obesity rates are significantly higher than in the general population. The increased prevalence is linked to a variety of factors related to both cognitive and adaptive functioning impairments.
And
Children and youth with intellectual and developmental disabilities (IDD) face up to 1.8 times the risk of being overweight or obese as their typically developing peers. One U.S. study of children aged 10–17 found the obesity prevalence to be nearly double (28.9% versus 15.5%) after adjusting for factors like age, sex, and poverty.
How well this extrapolates to adults with normal or low-normal IQ functioning is unknown, but I suspect it is continuous or on gradient.