Processed foods are easier for your body to break down because they’re stripped of fiber and nutrients — so your body doesn’t have to work as hard, which means fewer calories burned.

The sandwich made with real bread and cheese has about three times more fiber than the one made with white bread and processed cheese — and that extra fiber might make your body work harder to digest it.

Even though the whole-food sandwich had a bit more protein (which burns more calories), that alone couldn’t explain why it burned almost twice as many calories — so the processing must be the real reason.

Whole-food sandwiches have way more fiber — like 3 times more — which might make your body work harder to digest them and absorb fewer calories.

Consuming whole foods increases postprandial energy expenditure compared to isoenergetic ultraprocessed foods due to higher digestive effort and reduced thermodynamic efficiency.

Foods like cookies, chips, and sugary cereals are designed to be eaten quickly and taste super good, so people eat more before feeling full than they do with whole foods like fruits or beans.