Since 2004, the number of UK adults on low incomes who face hunger has likely almost doubled, suggested an analysis of survey data published online in the Journal of Epidemiology & Community Health.
The steep rise in UK food bank use in recent years has pushed household food insecurity back onto the public health agenda, say the researchers.
But little is known about the factors driving it, and whether it has increased during a period of austerity and welfare reform, or simply been exposed by the new availability of food banks.
The F&Y Survey included 3118 adults aged 16+ living in England, Wales, and Northern Ireland, while the LIDNS targeted the 15 per cent most deprived households in the UK.
Analysis of the F&Y data showed that around 1 in 5 adults (21%; 10.2 million people) in England, Wales, and Northern Ireland experienced some level of food insecurity in 2016. For nearly 3 per cent, this was severe, meaning that they likely went without food.
Several groups were at heightened risk of food insecurity. These included adults up to their mid 40s, those with children, those who didn't identify as white, and adults with low educational attainment.
Nearly one in three adults with children under the age of 16 was food insecure.The risk was greatest among the unemployed, those with long term conditions or disabilities, and those on the lowest household income.
To explore trends over time, the researchers compared 335 respondents in the lowest income bracket from the F&Y survey with respondents in the LIDNS, a process which matched people with similar socioeconomic and demographic features in both surveys.
Their calculations showed that between 2004 and 2016, food insecurity among the least well off almost doubled, rising from just under 28 per cent to nearly 46 per cent, after taking account of potentially influential factors.
The rise was even steeper among those living with a longstanding illness or disability just over 53.5% of whom experienced food insecurity in 2016.
This is an observational study, and as such, can't establish cause, added to which the people in each dataset were not the same in both time periods and 'low income' was defined differently in both surveys.
But if anything, the observed increase in food insecurity among those on low incomes is likely to be an underestimate, because people in the 2004 sample faced a greater degree of material deprivation than those in the 2016 sample, the researchers point out.
The scale of food insecurity in the UK is larger than recent food bank data suggest, and affects those who are already at risk of poor health, they highlight, suggesting that welfare system changes may help to explain the figures.
"While the Great Recession also occurred between 2004 and 2016 and may have contributed to a rise in food insecurity at that time, by 2016 the UK was no longer in recession. By contrast, welfare reform continued, the effects of which were keenly felt by those with longstanding illnesses," they write.
"The rising vulnerability to food insecurity observed between the 2004 LIDNS and F&Y survey suggests that the poorest in the UK are worse off today," they add.
And they conclude: "Food insecurity has certainly always existed in the UK, but in light of the welfare changes that occurred over this period, it is possible the current social security system is providing increasingly inadequate protection from food insecurity for more and more people."