More than 18 percent of U.S. adults claim they do not have access to adequate food from day to day, according to a new paper, which more than doubled between 1999 and 2016. The result: Higher obesity.

People got fat from not enough food?

There are obvious confounders, namely recall bias - and it's hard to reconcile an obese person stating on surveys they don't get enough to eat with biological reality. Scientists know that the only diet that really works is fewer calories. In 100 percent of studies people who consume fewer calories than they burn lose weight. They don't gain it eating less food. 

Just a hundred years ago if you were fat you were probably rich. Gout was a disease of the rich, it was rare in poor people. Today, the joke is that now you have to be rich to be thin, because it takes money for gym memberships, personal trainers, and liposuction. Modern science and agriculture have made it possible for food to be affordable for everyone so, yes, for the first time in human history poor people can afford to be fat. Yet in the greatest country in the world, an alarming amount claim they do not get enough food.

The survey responses from the National Health and Nutrition Examination Survey, which asks 5,000 people about lots of things, were nine two-year cycles of data, and found that among those included (46,145 total respondents over the period, mean age 46.9 years), nearly 20 percent of everyone except thin, white men and Asians claimed food insecurity. Obese people, women, Blacks, and Hispanics all claim inadequate amounts of food. 

The survey found that 35 percent of Hispanic adults reported inadequate food by 2016, up from 19.5 percent when the survey began.  Among women, the number claiming they don't have enough food went from 8.7 percent to 19.2 percent. For actual examinations, the authors used Body Mass Index, which is a simple ratio of height and weight, and waist circumference, but since this is population data that is reasonable. 

Since food insecurity is, at heart, a lack of calories, is it instead what people and demographers looking at surveys may believe about food insecurity - not enough food - are different?

No one is arguing that poor people are being showered with money to buy food and that they are getting fat and want more. Instead, food insecurity may be temporary. During the COVID-19 pandemic, with tens of millions more out of work due to concerns about spreading the virus, money will be a struggle so people taking a survey today might report worries about food - especially if they are already obese. Yet knowing that there are numerous confounders the authors still create an association between food insecurity and obesity - which is bordering on impossible - and claim statistical disparities in specific subgroups, such as sex and race/ethnicity, are meaningful when the same people were not used for each period. So they can't be compared.

These kinds of survey analyses can't get into cause and effect but people will speculate just the same. The authors suggest pushing off more interventions on already harried physicians, for example, when physicians would like to stop being told to be confrontational and judgmental and go back to being trusted guides. Though policymakers may want it, most doctors don't want to have to ask you about whether or not you own a gun and tell you to change your ways because epidemiologists can link anything to anything in 2020.

They certainly don't want to ask poor, obese people if they are getting enough to eat.