Question about calories absorp tion?????

I think I read some where that when you have the gastric bypass surgery you loose weigh in part because your body doesn't absorb the whole amount of calories you eat. Is it thruth?

With bypass, you malabsorb some of the fats and carbs (and nutrients) you consume...and since they contain calories, yup - you would malabsorb some of the calories. The problem is that it will vary from person to person on how many calories you malabsorb. The more bypassed, the more you malabsorb, but also the more nutrients you malabsorb too. It's a trade-off.