you do know whether you gain or lose weight has to do with calories consumed? 100 calories of american bread is no different weight gain wise versus 100 calories of french bread.
The usual macronutrient values (9kcal/g fat, 5 kcal/g EtOH, 4kcal/g carbs and protein) are surprisingly decently calibrated for metabolic inefficiencies.
They do not, however, take into account hormonal responses, which are probably quite a bit more important than once assumed. So there's that.