Previous studies have shown a link between body mass index and socioeconomic status, wherein children from low-income families are thrice more likely to be obese than their richer counterparts. Some studies also showed that being poor could lead to shorter stature and higher BMI as a consequence of factors including poorer diet.
However, it was not clear if the reverse was true. Could the opposite height and BMI influence outcomes such as job prospects, income and education levels? Does a person's height or size matter when it comes to socioeconomic status?
A Wide Gender Pay Gap
A new genetic study from Exeter University suggests that it does matter. Apparently, men who are taller and women who are slimmer earn more than those who are shorter and overweight, researchers said.
For a woman whose genetically predicted weight is 28 pounds or 12.7 kg heavier than another woman of the same stature, she is estimated to miss out on nearly £3,000 or about $4,269 every year.
Not only that. For a woman who has the same CV, same intellect and same background, becoming 14 pounds or 6.35 kg heavier would make her lose out on £1,500 or $2,135 per year.
If you took a 5'10" man and make him 5'7", he would also lose out on £1,500 or $2,135 per year.
Professor Timothy Frayling, co-author of the study, said that while their findings provide the strongest evidence for the causal link between BMI, height and socioeconomic status, this won't apply in every case as there are other factors at play.
Frayling said any men who are shorter and women who are overweight can still become very successful. Still, science must ask why the pattern in which taller men and slender women earn more occurs.
"Is this down to factors such as low self-esteem or depression, or is it more to do with discrimination? In a world where we are obsessed with body image, are employers biased? That would be bad both for the individuals involved and for society," said Frayling.
The Mendelian Randomization
The new study, which is issued in the British Medical Journal, used an approach called the Mendelian Randomization to analyze the link between BMI, height and socioeconomic status. Frayling said it is similar to doing a randomized control trial.
The team used data from United Kingdom's Biobank, and measured genetic variants relating to BMI and height in 119,669 men and women who were aged 40 to 70. They used five socioeconomic markers: job class, annual household income, the chance of getting a degree, duration of education and a level of deprivation metric known as the Townsend deprivation index.
Professor George Davey Smith, who was not involved in the study, said the findings do not mean that genes relating to height and BMI have specific biological effects on income, just that they have social effects.
It was striking to see the influence of height on annual income, researchers said. For every 2.5 inches of height, the annual income increased by £1,580 or $2,248 for men. It was smaller for women.
When it comes to BMI, annual household income and the Townsend deprivation index were influenced by trait among women.
Other findings, however, showed weaker links. Although height had an influence on job type for both genders and small influence on educational outcomes for men, BMI had a small role in affecting both outcomes.
Neil Davies of University of Bristol finds the results interesting.
"These results are consistent with small causal effects of height and BMI for some of the outcomes, but actually for others there is really quite compelling evidence that the associations that we see in the population are unlikely to be driven by height and BMI," said Davies.
Meanwhile, Frayling said it might be due to the smaller number of genetic variants for BMI compared to height, and the limitations in estimating socioeconomic outcomes.
"We can't say too much about the negative findings because that might just be a lack of data," he added.
The study did not explain how BMI and height might drive socioeconomic status, but authors suggest that there are other social factors such as self-esteem to discrimination. It also had limitations. The participants were from a diverse range of backgrounds, and social perceptions could vary from place to place.
"In past populations and some populations today being heavier was actually positively valued," added Davey Smith.
