Nutritional expert Miguel Martinez-Gonzalez of the University of Navarra in Spain analyzed the food consumption of more than 9,000 Spanish university graduates.
The study found people who combined white and whole-grain bread were not more likely to become overweight or obese. People who ate more than three slices of bread a day were 40 percent more likely to add on the pounds than those who only ate one portion of white bread a week.
"The issue is that white bread is made with highly refined flour which is rapidly absorbed as sugar," Martinez-Gonzalez told the Independent.
"Essentially it is equivalent to a high consumption of sugar. The problem is similar to what we see with soft drinks, their sugars are rapidly transformed into fat. A sensible recommendation would be to switch to wholegrain bread, especially for people who usually consume a lot of bread."
The findings were presented at the European Congress on Obesity in Bulgaria.