Processed foods make us fatter and are linked to a higher risk of cancer. Here’s what science suggests we should eat instead.

• Eating processed foods can lead to weight gain and is linked to higher rates of cancer, heart disease and early death.
• But it can be difficult to avoid these items when we’re busy or looking for something cheap to eat.
• Researchers at the National Institutes of Health recently developed unprocessed menus to feed patients at their diet research center. People who ate these meals lost weight and consumed less. 
• Those unprocessed-food menus included scrambled eggs with potatoes made from scratch, chicken, fish, bulgur, Greek yogurt, nuts, and lots of fresh fruit and vegetables.

• Visit Business Insider’s homepage for more stories.

It’s no secret that processed foods are bad for us. A recent study from Italian researchers found that eating more processed food was linked to an increasingly higher risk of dying from heart disease and stroke. 

In particular, ultra-processed foods – like processed meats, soda, breads, and pastries – are loaded with additives like sugar, salt, and preservatives that are linked to worse health. 

But there are alternatives. In 2019, a rigorously controlled study from the National Institutes of Health, fed 20 men and women a diet of ultra-processed foods like hot dogs, muffins, canned ravioli, and chicken salad for two weeks. They gained an average of 2 pounds, and consumed about 500 extra calories every day, compared to a different two-week period in which the same people followed an unprocessed meal plan.

The scientists behind the study found that this discrepancy arose because patients who were fed processed meals tended to overeat, even though researchers controlled for how much salt, fat, sugar, protein, fiber, and carbohydrates each meal contained (regardless of whether it consisted of processed versus unprocessed items).

“This is the first time that we can actually say that there’s a causal relationship between something that’s independent of the nutrients … that is driving these differences in calorie intake and weight gain,” lead researcher Kevin Hall told Business Insider.

His team isn't yet sure why processed food makes us hungrier, but they have a few educated hypotheses. For one, they think the difference in calorie consumption might have something to do with the ways that fresh foods trigger hormones that regulate our appetite (ghrelin), and suppress hunger (PYY). Additionally, people tend to eat unprocessed foods more slowly, which gives our body more time to register that we're full before we overeat. 

Beyond its link to overeating, a diet heavy in processed food is also linked with all kinds of other health problems, according to previous research: People who consume it regularly are more likely to get cancer and die quicker than others.

Given that stark comparison, here's how to determine what to seek out and what to avoid.

The difference between processed and unprocessed food

Researchers classify "ultra-processed" foods as items that are generally factory-made and come laden with additives and preservatives like sweeteners and thickeners. Generally, these things are packaged in plastic or cans. You're likely to see "high fructose corn syrup" on the ingredient list of an ultra-processed food item, or perhaps some interesterified oils (replacements for trans fats, which are now widely banned). 

The Italian researchers in the most recent study found that processed meat, pizza, and cakes were the most common ultra-processed foods in the diets they studies. 

Unprocessed food, on the other hand, involves raw ingredients like fresh produce, unflavored yogurt, home-cooked meat, and whole grains.

But food items don't have to be completely fresh to be considered unprocessed. In the NIH study, the researchers relied on the NOVA food-rating system, which designates foods as unprocessed if they are edible parts of plants (including nuts), animals, fungi, algae, or water. So it's fine to freeze, boil, ferment, or refrigerate ingredients. But unlike their processed versions, unprocessed foods are not cured or pre-salted.  

The study authors described and photographed the meals they fed their 20 participants - both during their processed-food weeks and the time spent on a fresher eating plan.

Here's one of the processed breakfasts that the participants ate in the lab:

One of the processed lunch meals was a tasty-looking quesadilla made with deli turkey, cheddar and jack cheeses, and refried beans from a can. That might be disheartening, since it's very likely to be similar to meals you'd make at home. So is a chicken salad sandwich made with canned chicken, pickle relish, and mayonnaise - one of the ultra-processed dinners.

While on an unprocessed diet, on the other hand, the participants ate more produce and skipped sides like tater tots. Here's what a day's worth of unprocessed meals looked like in the lab:

Unprocessed breakfast: a yogurt parfait

Unprocessed lunch: spinach salad

Unprocessed dinner: stir-fried beef tender roast 

After two weeks of meals like these, participants managed to shed an average of 2 pounds.

Read more:

A public health researcher is warning that ultra-processed foods like white bread and burgers could damage your heart

Eating a lot of processed foods could cause your body to age more quickly, a new study suggests

Dietitians share their most hated foods, from deli meat and energy drinks to red wine