U.S. obesity rates started to soar in the 1970s and show no signs of leveling off, never mind falling. “The question is: What changes in the food environment can explain the increase?” says Kevin Hall, a senior investigator at the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK).

You needn’t look too far for an explanation.

What a toxic food environment looks like

“Portion sizes and the availability of highly processed, highly caloric food have grown dramatically,” says Kelly Brownell, a professor of public policy, psychology, and neuroscience at Duke University.

“And we have fast food restaurants, drive-in windows, vending machines, and food courts, and food available in drug stores, gas stations, and essentially every venue.”

One way to think about your food environment: “How far are you from a doughnut?” asks Brownell. “How close is a Dunkin’ Donuts or a coffee shop or a supermarket or a 7-Eleven that sells doughnuts? That’s just one example.”

And that 24-hour, all-you-can-eat buffet of inexpensive, unhealthy, pervasively marketed food has had an impact.

“When I was young, nobody ate in their car, unless they packed sandwiches for a long trip,” says Brownell. “We ate three meals a day and maybe a snack. Now people eat all day long.”

What’s more, the nature of the food we eat has changed.

“Our food is highly processed by sophisticated companies that want to maximize consumption,” says Brownell.

“They’re processing food in ways that make it difficult to put the brakes on eating. These foods are hijacking the brain in a way that undermines personal decision-making, and they’re creating a health hazard.”

Scientists are trying to figure out why—and which—processed foods lead us to overeat.

Meanwhile, “we should do everything we can to create a healthy food and physical activity environment to prevent obesity,” says Brownell, “just as we do with problems like heart disease, depression, or alcoholism.”

And people who have obesity deserve the same respect, attention, and care as those with any illness.

“The overriding aim should be to treat people with compassion, kindness, and effective medical care,” says Brownell.

Why obesity is so hard to treat

Until now, effective treatments have been scarce.

“Persons with obesity generally try hard to lose and keep weight off but often don’t succeed,” says Julie Ingelfinger, professor of pediatrics at Harvard Medical School.

“In many people with longstanding obesity, there are physiological changes that counteract weight loss no matter what one does.”

For example, when people lose weight, the body “defends” its former bigger size by boosting hunger, enabling muscles to burn fewer calories, and burning fewer calories overall when at rest.

“It’s not that people are lazy,” explains Ingelfinger. “It’s not only that our way of life has become more sedentary and that our food and the way we prepare it have changed, but that obesity is a complex condition that is very hard to treat.”

That’s why many experts are excited about several new drugs that may help people lose weight and keep it off.