Bread and rice are both sources of carbohydrates. Once eaten and digested, they are both converted to sugar (or glucose) in the body. When eaten inappropriately, both of them can lead to weight gain and when eaten appropriately, either of them may result to weight loss.
Eating bread per se or simply switching from rice to bread will not cause anybody to lose weight. Weight loss will only result when the total number of calories consumed (regardless of the source of calories, whether carbohydrates, simple sugars, protein or fats) is less than the total amount of calories burned by the body.