Your sister sounds like she's read/heard one too many Adkins-like diet promos.
Your body has three classes of fuels it runs on: carbohydrates, proteins, and fats.
In that order they are burnt, easiest to hardest. That is, your body has to "work harder" to turn fat into energy, than it has to work to turn carbs into energy. So carbs, when available, are burnt by the body first. If you deprive your body of carbs (the idea behind Adkins diets), it will be forced to burn protein or fats, which should in theory, cause you to lose weight.
So, will eating a lot of bread cause you to put on weight? Well, yeah, eating too much of anything
will cause your body to preserve the energy you've eaten by converting it to fat and storing it for later. However, because carbs are your body's primary fuel, you have to eat a lot more of them to eat too much (because they are so readily burnt), than you do fat sources or protein sources. Hence their importance on the food pyramid, at the bottom level:
So, you're both right. Eating too much bread will cause you to gain weight.
Eating a balanced diet that includes bread won't.
(BTW, This is all grade 5 health class stuff)
Edited by shakey_snake, 08 December 2007 - 09:27.