Poverty has a way of rearing its ugly head, slipping into the cracks in people's lives when they're young and then re-emerging later in life. Sometimes it happens in ways that are easily observable — what poor babies are fed, for instance, has been shown to alter what they crave as adults, creating life-long affinities for foods that might be better left uneaten. But sometimes the influences are hidden, and all the more insidious as a result.

A team of researchers, led by Sarah Hill, who teaches psychology at Texas Christian University, believe they have uncovered evidence of one such lingering effect. Specifically, Hill and her colleagues found that people who grow up poor seem to have a significantly harder time regulating their food intake, even when they aren't hungry.

“We found that they eat comparably high amounts regardless of their need,” said Hill.

The researchers, interested in exploring why obesity is more prevalent in poorer populations, devised three separate experiments, which tested how people from different socioeconomic backgrounds behaved in front of food.

In the first, they invited 31 female participants into their lab, who were asked how long it had been since they had eaten, and how hungry they were. They were then given snacks (cookies and pretzels), which they were free to eat or leave be, as they pleased. When they were finished, Hill and her team measured the number of calories each consumed. The discrepancy between how the participants ate was alarming.

Those who grew up in higher socioeconomic households exhibited normal consumption behavior — eating when they were hungry, saying no thank you to the snacks when they were full. Those who grew up in lower socioeconomic households, meanwhile, ate no matter how hungry they were. The chart below, plucked from the study, does a good job of depicting the difference between the two groups.

Fig. 1. Results from Study 1: total number of calories that participants consumed as a function of energy and need and childhood socioeconomic status (SES). For both energy need and SES, high refers to values 1 standard deviation above the mean, and low refers to values 1 standard deviation below the mean. Error bars represent +/-1 SEM

A single experiment, however, isn't nearly enough to establish a convincing connection. So they took it a step further.

This time they invited 60 female participants, each of whom was asked to refrain from drinking or eating for five hours. Half of them were given Sprite, a caloric beverage, while the remaining half sipped on sparkling water, which has no calories. Then, they too were given snacks (cookies and pretzels), which they were free to eat or leave be, as they pleased. And, once again, what Hill and her team observed was eye-opening.

“It's incredible, it's as though the soda didn't register for those whose socioeconomic status as a child was low,” said Hill. “It went down like water.”

Those who grew up in higher socioeconomic households ate far less when they had consumed a Sprite, while those who grew up in lower socioeconomic households ate regardless of the beverage they had been given. The chart below, also taken from the study, shows how differently the two groups behaved.

Fig. 2. Results from Study 2: total number of calories that participants consumed as a function of drink condition and childhood socioeconomic status (SES) as indexed by the single-item measure. High and low SES refer to values 1 standard deviation above and below the mean, respectively. Error bars represent +/1 SEM.

In the third and final experiment, the researchers replicated the second, but added two tweaks. They invited 82 participants, which included men this time, and measured each participants' blood glucose to see if their blood sugar levels mediated food intake as they should.

Yet again, only those who hadn't grown up in poor households seemed to properly regulate their food intake.

Fig. 4. Results from Study 3: total number of calories that participants consumed as a function of postmanipulation blood glucose level and childhood socioeconomic status (SES). For both postmanipulation blood glucose level and SES, high refers to values 1 standard deviation above the mean, and low refers to 1 standard deviation below the mean. Error bars respresent +/1 SEM.

“We expected to observe these differences, but not this clearly or consistently,” said Hill. “I think it points to how the conditions poorer children face when young could be leading them to behave in ways that promote things like overeating and obesity.”

Hill singles out childhood poverty, because she and her team asked participants not only for their socioeconomic statuses as children, but also their current socioeconomic statuses as adults, and, rather incredibly, the abnormal eating patterns only correlated with the former.

“I was very surprised by this,” she said. “We really thought there would be an association with both.”

What's going on?

The reason why people who grow up in poorer households seem to have trouble controlling how much they eat when they're not actually hungry is not entirely clear. But there are likely a few things going on.

For one, Hill posits that growing up in poorer households, which tend to have less educated parents, could lead to less of an awareness of one's body and the changes that it undergoes. “If they aren't in tune with their bodies, they might not be in tune with their bodily needs,” she said. “And that's kind of what the results suggest.”

There might also be a form of conditioning that's tied to the actual circumstances in which poorer families encounter and experience food. For those who never had to worry about a meal, foregoing a snack is no big deal — it's an afterthought. But for those who did, it could mean the difference between a good night's sleep and hours awake in bed.

“When you grow up in these types of environments, you’re effectively being trained to eat when you can instead of when you’re hungry,” she said. “Something about that experience could be leftover.”

Traci Mann, who teaches psychology at the University of Minnesota and has been studying eating habits, self-control and dieting for more than 20 years, has a slightly different theory.

People, she says, begin life perfectly capable of starting and stopping to eat when they are hungry and when they are full. “Babies can do it — breast feeding babies do that exactly (as long as the mom doesn't mess it up) — and small kids as well.”

As the years go by, we tend to lose this ability to some extent, forcing us to rely on other cues—like memory. Certain people, however, lose the ability faster and more broadly than others. A perfect example are people Mann calls “chronic dieters,” who are constantly restraining what they eat. By depriving themselves of calories, they end up triggering biological changes in their bodies that actually make it harder for them to resist food. And this, she says, is likely what's happening with those born into lower socioeconomic statuses.

“It's not terribly surprising that a childhood of caloric deprivation (due to financial issues) would lead to the same long-term problems that you see among chronic dieters,” she said. “Essentially, eating when not hungry.”

However similar the pattern of behavior, the implications are still unsettling.

If there is such a gap between how poor and rich children interact with food that carries over to rest of their lives, it complicates our understanding of why here in the United States, contrary to international trends, poor people are far more prone to obesity than their wealthier counterparts. Many have posited that it's not how much poorer households are eating, but what they are eating that has caused this trend. And there is plenty of reason to believe there is truth to this—studies have shown, after all, that lower income families choose substantially less healthy foods than others. The harms of unhealthier diets, however, are all the more nefarious when they're coupled with a fractured ability to regulate eating.

Hill warns that her team's findings are still preliminary. “We don't know exactly what the mechanism is, or how self-aware the people who eat even when they aren't hungry are,” she said. “We need to pursue more research to figure out what is causing these troubling patterns of behavior.”

She also says that just because the pattern exists, doesn't mean it's not something we can change. “There's no reason to think we can't help them override this.”

But the fact that the patterns exists steepens what we already know to be an uphill climb for those born into poverty in the United States. The tentacles of poverty touch many different aspects of people's lives. Food is a particularly apt example — food inequality, whereby America's wealthiest people eat well, while the country's poorest eat, well, poorly, is not only real, but worsening — but it's hardly the only one. Poverty has, for instance, been shown to shackle those who are born into it, severely limiting their ability to succeed in society — socially, academically, and financially.

Increasingly, it seems the key to breaking the cycle of poverty might lie in understanding that the gap begins to grow at a very early age, cementing itself in ways that make it very difficult to untangle. And there are few things as stark as the difference between how poor and rich kids develop relationships with food.