What determines the accumulation of fat is the excessive consumption of the different nutrients that provide energy, namely proteins, carbohydrates and fats.
Like any food, it depends on the amount consumed. There must be a balance between what is ingested and what is spent, in terms of energy.
Consumed in moderation and as part of a varied and balanced diet, bread is not fattening.
Preferably, choose wholemeal bread over refined flours, as they are richer in fibre and are more satiating.