The white flour used to bake white bread has been stripped of its outer shell (the bran), which depletes the grain's feel-full fiber content. Eating it spikes your insulin levels, Dr. Decotiis says.
In a recent Spanish study, researchers tracked the eating habits and weights of more than 9,000 people and found that those who ate two or more servings of white bread a day were 40% more likely to become overweight or obese over a five-year period compared to those who ate less of it.