Landmark Study Links Ultra-Processed Food With Overeating, Weight Gain

In what has been called the first study of its kind, researchers have found that consuming 'ultra-processed' foods results in overeating and, as a consequence, weight gain. The findings result from a small trial conducted by the NIH's National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK); they build upon past research that found a link between highly processed diets and health issues.

The study was fairly small, involving around 20 adult participants who ate ultra-processed foods and minimally processed meals. The meals — both processed and relatively whole varieties — contained the same number of calories and percentages of carbohydrates, fat, sugars, and fiber. Participants were allowed to eat as much food as they wanted during the study.

Researchers describe the experiment as "tightly controlled" with results that demonstrate "a clear and consistent difference" between eating highly and minimally processed meals. Over the course of the study, the consumption of highly processed meals resulted in overeating and weight gain, while minimally processed meals resulted in less eating and more stable weight.

What, in the context of this study, is considered 'ultra-processed' food? The NIH lists some examples of the meals given in both categories — turkey bacon and a bagel with cream cheese is an example of an ultra-processed meal, whereas oatmeal with walnuts, bananas, and skim milk was considered minimally processed.

Foods that contained certain common ingredients usually only found in manufactured products, including high fructose corn syrup and hydrogenated oils, fell in the ultra-processed category. Unfortunately, the reason behind the overeating remains a mystery. The study's lead author Kevin D Hall, PhD, said:

We need to figure out what specific aspect of the ultra-processed foods affected people's eating behavior and led them to gain weight. The next step is to design similar studies with a reformulated ultra-processed diet to see if the changes can make the diet effect on calorie intake and body weight disappear.