A stable component of body mass index appears linked to a person’s likelihood of experiencing social discrimination, according to a study published in Adaptive Human Behavior and Physiology. Using genetic prediction models, the study found that higher trait-BMI was linked to worse discrimination and declining life satisfaction among older adults.
Overweight and obese people are frequently stigmatized as lazy and lacking in self-discipline. This stigma leads overweight people to be discriminated against as early as childhood. Evidence suggests that weight discrimination induces further social and economic costs, such as lower achievement in school and lower wages. These disadvantages can then lead to psychological distress and poor life satisfaction.
Body mass index (BMI) is a measure of body size which is calculated based on a person’s height and weight. Higher BMI has been consistently linked to worse discrimination, especially among women. Building on this research, study author Aniruddha Das wanted to consider whether a genetic component of BMI might be linked to discrimination.
“As a sociologist, the one thing that strikes me strongly about the whole preventive medicine idea is the notion that individual behavior is under individual control,” explained Das, an associate professor at McGill University. “The same pattern appear in popular conceptions of healthcare responsibilities — this idea that people are responsible for what they do.”
“That may not always be the case — whether due to social constraints or genetic impulse. Rather than ‘blaming the victim,’ we need bottom-up approaches that actually work in the lived reality of people’s constraints. Obesity seemed a good way to cut into the topic.”
As Das explains, biological models differentiate between state-BMI and trait-BMI. While state-BMI can fluctuate with lifestyle changes, trait-BMI is driven by biological factors and may involve an individual set point. Owing to its genetic roots, trait-BMI should be resistant to change despite a person’s best efforts — suggesting particular implications for life satisfaction.
Das conducted a population study to explore whether older adults with higher trait-BMI would report more frequent daily discrimination and lower life satisfaction. Data was obtained from the Health and Retirement Study (HRS), a representative survey of U.S. residents over 50 that has been administered every two years since 1992.
Participants’ self-reported height and weight measurements were used to calculate BMI. Trait-BMI was then obtained using genetic prediction models and polygenic scores (PGS) — estimates of a person’s genetic risk for a trait — from the HRS 2010 and 2012 waves. Perceived everyday discrimination was measured by asking participants how often they experienced certain events in their daily lives, such as being harassed or receiving poor service in a restaurant. Self-reported life satisfaction was assessed using a 5-item scale with items like, “In most ways my life is close to ideal.”
An analysis of the results revealed that higher trait-BMI was linked to higher daily discrimination. Next, there was evidence that higher trait-BMI was associated with worse life satisfaction over time. Life satisfaction change scores were calculated based on participant data obtained from waves 2010 to 2014, and 2012 to 2016. At each wave, higher genetically predicted BMI was associated with a decline in life satisfaction over 4 years. Interestingly, these associations were not consistently mediated by discrimination.
“Genetically predicted body mass or ‘trait BMI” — weakly if at all under a person’s control (i.e., ‘not their fault’) — seems linked to either the fact or just the perception that they have been discriminated against,” Das told PsyPost. “That fact doesn’t seem to ‘matter’ much, though, given that it doesn’t strongly mediate worsening of life satisfaction among those with greater trait BMI. Still, as a social fact, it ought to bother us.”
However, in contrast to what one might expect, the link between trait-BMI and discrimination did not appear to be moderated by gender.
“Women with greater trait BMI were not more likely than men to face discrimination,” Das said. “This flies in the face of a lot of literature in the social sciences on women’s greater vulnerability to such social pressures.”
The fact that trait-BMI is linked to a drop in life satisfaction is concerning, the author says, since preventative health methods tend to emphasize lifestyle changes as a strategy to combat obesity. These types of interventions may not be effective if trait-BMI is a stable trait. “Indeed, reaching a BMI representing a slender ideal may not be feasible for everyone,” Das wrote in his study.
But the researcher noted that his findings, at this point, are only “suggestive.”
“Stay tuned,” Das said. “Biodemographic research is only just beginning to take off.”
The study, “Genetically-predicted trait-BMI, everyday discrimination and life satisfaction among older U.S. adults”, was authored by Aniruddha Das.