Poor people comfort-eat fattening foods to counter their bruised self-esteem, according to new research by Scottish academics.
The international study, led by the University of St Andrews, is the first evidence of psychological links between poverty, inequality and increased calorie intake.
The findings show people who perceive themselves as poor are likely to eat more.
It also suggests individuals consume more to “self-soothe” a sense of anxiety when they feel unequal to others.
The most recent government data shows 65 per cent of Scots aged 16 and over were overweight in 2014, including 28 per cent who were obese.
The proportion who are overweight or obese among both sexes has been rising for the past two decades, with the steepest increases between 1995 and 2008.
The new research provides the first experimental evidence that poverty and inequality can cause obesity through increased consumption of high-calorie food, and that psychological mechanisms link economic conditions to eating behaviour.
University of St Andrews lecturer Dr Boyka Bratanova, who led the study, said: “Feeling poor and feeling unequal can simultaneously influence eating behaviour, pushing people to approach high-calorie food and consume larger amounts of it.
“It appears that humans and animals respond similarly to harsh and scarce environments, and this response takes the form of pre-emptive increase in food consumption.
“Inequality, on the other hand, evokes a sense of anxiety, and this is true both for the disadvantaged and for the advantaged.
“The disadvantaged are worried that others will look down on them and see them as inferior; the advantaged are worried that others may envy them and challenge their privileged position.
“This social anxiety in turn pushes people to consume larger amounts of food high in sugar and fat as a way to soothe their emotions.”
Dr Bratanova hopes that the findings will be used to re-evaluate measures aimed at prevention and treatment of obesity.
She has hit out at the UK government’s planned sugar tax on soft drinks, claiming it is “unfair” and will hit the poorest people the hardest.
She said: “People who feel poor would probably continue to eat high-calorie food at a similar rate, as this food provides them with a higher caloric yield. This is hard to overturn, because the urge comes from a perception of their economic reality.”
She said that campaigns based around education are also likely to instead induce guilt.
Dr Bratanova added: “Taken together, the poor in a society seem to have it the worst – they carry the burden of poverty, suffer emotionally from relative deprivation, pay higher proportion of their incomes in consumption tax, and feel guilty and inadequate because of their eating behaviour.”
She said: “Addressing the root causes – poverty and inequality – would be the ultimate solution of the obesity crisis.”