Highly Processed Foods Linked to Weight Gain

Highly processed lunch: Spam sandwich with American cheese on white bread, potato chips, and diet lemonade Hall et al., Cell Metabolism

A study found that when people consumed a diet of highly processed foods, they took in more calories and gained more weight than when on a diet of minimally processed foods.

Researchers compared the effects of a highly processed and a minimally processed diet in 10 men and 10 women residing for four weeks at the NIH Clinical Center. Each diet lasted for two weeks. People received three meals per day plus snacks. They could eat as much or as little as they wanted.

Processed foods usually have a lot of calories, salt, sugar, and fat and are low in fiber, but the researchers matched the meals for these nutrients.

The highly processed diet had foods like canned ravioli, hot dogs, chicken nuggets, pork sausage, and tater tots. The minimally processed diet had foods like salad, grilled beef roast and vegetables, and baked fish. People noted that the diets both tasted good and were satisfying.

On the highly processed diet, people ate more calories and gained an average of 2 pounds. On the unprocessed diet, they ate fewer calories and lost about 2 pounds.

The results support the benefits of unprocessed foods. But the researchers note that processed foods can be difficult to avoid.

“Just telling people to eat healthier may not be effective for some people without improved access to healthy foods,” says NIH obesity expert Dr. Kevin Hall, who led the study.

More studies are needed to better understand how processed food affects weight.