Nancy Roman, president and CEO of the Capital Area Food Bank, has been overwhelmed by cake. Week after week, dozens of frosted, layered confections arrive at her warehouse. A 5-year-old might think this is a dream come true. But for Roman, it’s a nightmare.

The cakes are donations meant to be passed along to the food bank’s end users — more than half a million residents of Washington, DC, and its Maryland and Virginia suburbs who don’t have enough to eat. Like other low-income Americans, many of these folks struggle with obesity, diabetes, heart disease, and high-blood pressure. And lately, Roman has worried that sending them highly processed, sugary foods — which are energy-dense and nutrition-poor — isn’t going to help matters.

This autumn, the Capital Area Food Bank did something to address its "incredible exploding warehouse of sheet cakes": it began rejecting junk food donations — including the cake and other baked sweets, caloric sodas, and candy. It’s part of an effort to clean up their food supply, said Roman. "We have a moral obligation to not just get food to people — but the right food."

With the move, DC’s largest food bank joined a handful of others that are now turning away donations for the needy — from cookies to Kraft macaroni and cheese — on the basis of quality. These food banks are saying no to the salty, sugary, and fatty foods that will create a double tragedy for the hungry: driving up chronic disease in people who can’t afford healthy food.

It’s also the latest sign that more nutrition leaders — inside and outside of the health community — are beginning to take measures to address two seemingly unlikely bedfellows: hunger and obesity.

Why obesity so often stems from food insecurity

We often think about obesity as being related to having too much to eat. (The word comes from the Latin obesus — which means "having eaten until fat.")

But there’s a growing body of evidence linking food insecurity (having too little or uncertain access to food) to obesity — particularly among women. (The data on whether food insecurity is a risk factor for obesity in men and adolescents is more mixed.)

The idea isn’t new. In 1995, a case report tilted "Does Hunger Cause Obesity?" tracked an obese 7-year-old African-American girl who lived in a household that relied on food stamps. "At least two possibilities could explain the association of hunger and obesity in the same patient," the author wrote. "In this family, the increased fat content of food eaten to prevent hunger at times when the family lacked the money to buy food represents the most likely reason for the association of obesity and hunger. An alternative possibility is that obesity may represent an adaptive response to episodic food insufficiency."

Since then, researchers have come to accept this counterintuitive association — once called the "food insecurity obesity paradox" — and are finding that it has to do with a lot more than stocking up on fat.

Fruits and vegetables are more expensive than junk foods

There are several explanations for why food scarcity and obesity can coexist, and the first one to understand has to do with basic food prices.

"Historically, when we talked about the obesity-hunger paradox, it was described in terms of cost," said Hilary Seligman, an associate professor at the UCSF School of Medicine. "Healthy food, calorie for calorie, costs more."

As you can see in the chart below, when it comes to how many calories you get per dollar, sugar, vegetable oils, and refined grains deliver a higher bang for your buck than fruits and vegetables.

If your household income is low or you’re food-insecure, you’re probably going for the cheapest, highest-calorie options. The latter also happen to be designed to encourage overeating. But in the long run, it’s the nutrients in food (like fiber, vitamins, and minerals) that matter more for health than calories alone.

"To maintain adequate energy intake, many families with limited resources select lower-quality diets, including high-calorie, energy-dense foods," Angela Odoms-Young, an assistant professor of nutrition at the University of Illinois at Chicago, explains. Fruit and vegetable consumption also goes down significantly as food-insecurity status worsens.

So that means that at home, poor people aren’t getting enough quality food. Yet researchers have found that food donations too often fail to meet basic nutritional requirements. So when the needy turn to charities to get food, their options can be similarly limited.

A lack of access to healthy food promotes binge eating

There’s a second proposed reason for why hunger leads to obesity, and it’s also pretty easy to understand: A lack of access to food may cause people to binge eat when they’re worried about where their next meal is coming from.

"Those who are eating less or skipping meals to stretch food budgets may overeat when food does become available, resulting in chronic ups and downs in food intake that can contribute to weight gain," reads this 2015 review of the problem from the Food Research and Action Center. "Cycles of food restriction or deprivation also can lead to disordered eating behaviors, an unhealthy preoccupation with food, and metabolic changes that promote fat storage — all the worse when combined with overeating."

So bingeing is a coping mechanism that works in the short term — to create buffers between food abundance and food shortages — but may increase the risk of obesity in the long run.

Food insecurity is linked to stress — which is an obesity driver

Living in a food-insecure household is about the most stressful thing you can do, and obesity is highly related to stress.

"Lots of studies done in animal models find that if you stress an animal with a food insecurity–like state, they do release a bunch of different stress hormones," explained Seligman. "Over time they also develop obesity and insulin resistance."

That stress can also prime someone to want sugary, fatty, and other energy-dense foods. Here’s a nice summary of the science, according to a 2013 paper on food insecurity and chronic disease:

Evidence from animal models subjected to food scarcity as a stressor suggests that food intake is altered and a preference for high-fat, high-sugar foods is activated under stress conditions. Exposure to household food insecurity is associated with stress and depression, episodic food availability, household food shortages, and reliance on high energy-dense foods. A "new" model of comfort foods suggests that stress activates the hypothalamic-pituitary-adrenal axis, releasing cortisol which can alter metabolic processes. In addition to the stress pathway being activated, 2 other systems are activated: the hedonic (reward) pathway and memory. This comfort food model is based on observations that within a very short time period, animals learn that the high-fat, high-sugar foods are rewards that dampen the stress response. As a result, the animal seeks the same food the next time stress is introduced, even with much lower stress stimuli.

So those calorific foods mess with the metabolic response and reward system in the body, raising the risk of chronic diseases. Those foods are also just the kinds that happen to be cheap and readily available, especially at food banks that haven’t yet cleaned up their food supply.

How food banks can make a difference

Food banks are only one small part of the food system, but they interact with a group that is most vulnerable to food-related chronic diseases like obesity. So it should be clearer why some food banks are making an effort to offer quality calories, instead of just any calories that come their way through donations.

As Seligman said, "Everyone deserves access to healthy food, and to the extent that we can make that food available and easily accessible in every community in the US — and not just our wealthier communities — the better we will do at improving people's quality of life, helping children develop palates for healthier foods, and preventing obesity and diabetes down the line."

Making these changes won’t be easy. When Roman first floated the idea of the new policy, it wasn’t welcomed by all. "In the beginning, it took a lot of courage," she said. "There are a lot of people who feel you can’t offend the donors."

"We don’t want to be the food police. We believe people are entitled to eat cakes."

A big step involved getting retailers like Giant (which supply the food bank) on board. "They basically [do] the work of sorting out the bakery goods and not giving them as a contribution to the food bank," she said, adding that the many retailers have been really amenable.

Fully one-third of the food Capital Area Food Bank gives to the poor are now fruits and vegetables — a ratio that will now hopefully improve with the new policy. "We don’t want to be the food police," Roman added. "We believe people are entitled to eat cakes. But we want [ours] to be a balanced offering." If only other food banks would follow suit.