At last count, 74 percent of U.S. adults and 35 percent of children are overweight or obese. These numbers tick up every year.

“We are trying to understand the properties of our food environment that regulate appetite and cause people to overeat and gain body fat,” says Kevin Hall, a researcher at the National Institutes of Health.

Hall discovered that ultra-processed foods are the culprit. In a 2019 study, Hall offered 20 people largely unprocessed foods for two weeks and ultra-processed foods for two weeks. Unprocessed foods are fresh or frozen vegetables and fruits, beans, nuts, seeds, unflavored yogurt, pasta, oats, rice, no-sugar-added muesli or shredded wheat, etc. Ultra-processed foods include sugary drinks, chips, ice cream, chocolate, packaged breads, cookies, pastries, breakfast cereals, cereal bars, flavored yogurts, frozen pizza, instant soups, etc.

“People consumed an average of 500 more calories a day on the ultra-processed foods compared to the unprocessed foods,” says Hall. “That led them to gain two pounds on the ultra-processed diet and lose two pounds on the unprocessed diet.”

The meals in both diets had equal amounts of carbohydrates, sugar, fat, protein, and fiber. But, there was a key difference between the two diets: Beverages aside, the ultra-processed food diet had nearly twice the caloric density of the unprocessed food diet.

Calorie density is the number of calories in a given portion. It is the measure of how many calories are in a given weight of the food. For example, one pound of doughnuts contains over 2000 calories making it a calorically dense food item compared to one pound of grapes which contains only 306 calories.

Barbara Roll, director of the Laboratory for the Study of Human Ingestive Behavior at Penn State, performed a study where the participants ate 290 calories at an all-you-can-eat lunch buffet with chicken and rice casserole. One group got the casserole with a cup and a half of water, the other got the chicken and rice watered down into a soup. They started with the casserole and were offered to eat whatever else they wanted.  The group who sat the soupy casserole ate on average 400 calories less.

In other words, Roll says, “it’s better to eat your water, not just drink it. When you drink water, it empties out of your stomach more quickly.”

It’s not just soup. The best way to add water to your diet: eat more fruits and vegetables.

In a 2007 study, Rolls randomly assigned women with obesity to eat either less fat or eat less fat and eat more fruits and vegetables for a year. “The group that ate extra fruit and vegetables lowered their calorie density more, and they were eating a better quality diet.” The diet with the fruits and vegetables also made the participants less hungry.

“Companies are all about maximizing the allure of their products,” says Michael Moss, Pulitzer Prize-winning former New York times reporter whose book Hooked: Food, Free Will, and How the Food Giants Exploit Our Addictions. “One definition of addiction is a repetitive behavior that some people find difficult to quit… That perfectly fits our relationship to food, though it varies from person to person,” says Mr. Moss.

Instead of addiction, food companies use the words “craveability” and “likability”. Unfortunately, Moss explains, we are designed to put on lots of body fat and defend against any efforts to shrink it. In hunter-gatherer societies, extra body fat could make the difference between life and death.

This didn’t matter until about 50 years ago when the food industry changed the nature of our food. These companies now have scientists who spend their time devising formulas that create the biggest attraction in the brain. It starts with the three ingredients featured in Moss’s previous book, Salt, Sugar, Fat.

• Sugar -“The industry came up with the term ‘bliss point’ to describe the perfect amount of sugar in a drink or food that would send us over the moon. Not too little, not too much.”
• Fat – “In snack foods like potato chips, 50 percent of the calories typically come from fat, which gives them that melt-in-your-mouth phenomenon, which so much ultra-processed food has. You hardly even have to chew it.”
• Salt – “Salt is the flavor burst because it’s often on the surface of the food and the first thing that touches the tongue.”

Fat and carbs are in the foods that people find the most irresistible. Ashley Gearhardt, associate professor of psychology at the University of Michigan, points out that chocolate, ice cream, french fries are the foods most people overeat. Gearhardt explains that flavor enhancers and texturizes amplify the appeal of highly process foods.”

Variety is also compelling. Barbara Rolls did a study in 1982 that showed people eat about 15 percent more pasta if given a variety of shapes instead of just one.  “And when we serve sandwiches with four different fillings, people ate a third more than when they were served sandwiches with one filling…The appeal of variety explains the smorgasbord effect where you can feel completely full, but dessert comes along and all of a sudden your brains goes, ‘Ah, we can eat more.'”  Or think of the potato chip aisle that has more than 10 different flavors to choose from.

In Hall’s 2019 study, people ate the ultra-processed foods faster than the unprocessed foods. Unprocessed foods take more chewing. They have more intact fiber.

Studies show that TV ads influence food preferences and consumption, at least in children, according to the World Health Organization. “Companies know how to press those emotional buttons to get us to eat, even when we are not hungry,” says Moss. “The key is to create strong food memories by showing the product at the precise moment when our emotions are running high.”

The food industry has created more and more products that encourage us to snack during the day. “It’s basically a fourth meal,” says Moss. Snacks are ultra-convenient and usually able to be eaten while you are doing something else. When that happens, your brain is not paying attention to the signals from your stomach. In one study, people ate about 35 percent more pizza and 70 percent more mac and cheese while watching TV than while listening to music.

“The food industry is all about making products as cheaply as possible,” says Moss. “They use flavors that mimic the tastes and smells of the real thing. Their overall purpose is to keep their food as cheap as possible. Moss ask companies to help people by adding more fruits and vegetables. They cannot because if they “stuff a Hot Pocket with broccoli rabe, they lose the cheapness factor.”

Tips to help minimize ultra-processed foods and cut calorie density:

• Load your plate with fruits and vegetables. Big Portions! “We eat with our eyes and our brains,” says Rolls. “If we see a big portion, that sets us up to feel more satisfied. If a plate looks half empty, that sets us up to feel hungry.”
• Eat healthy fats like nuts and seeds which are calorie dense with water-rich food like fruits and veggies.
• Stick to water, coffee, tea or other calorie-free beverages.
• Cook your own food whenever possible.