<<What everybody seems to forget is that digesting food, particularly
difficult
to digest food like carbohydrate, consumes a lot of energy. This is why you
feel unenergetic after consuming a lot of carbo.>>

I haven't seen anything to suggest that carbs are anymore "difficult" or
energy-consuming that other macronutients like protein and fat.  In fact, it
can be argued that consuming protein and fat place greater demands on the
kidneys and liver.

Carbs readily liberate their glucose bonds (to various degrees of course),
increasing blood sugar levels.  The increase in blood sugar is one component
of "energy".

There may also be an addictive component to eating simple carbs as these can
temporarily increase beta-endorphin and serotonin levels in the brain.
Afterwards, neurorecpetors downregulate and serotonin and beta-endorphin
levels are lower than "normal".  In order to feel normal, or even high
again, one needs another carbohydrate "hit".

If you feel tired after eating "carbs", I suspect:
* food allergies/sensitivities (i.e., its important to determine which carbs
cause this affect)
* hyperinsulinemia/insulin resistance (muscle, liver and brain cells become
increasingly resistant to insulin (which carries glucose into these cells).
Thus, while blood sugar levels may be high, glucose in the cells may be
temporarily low; until the pancreas cranks up another whopping load of
insulin to *force* the insulin-glucose pair into the cells of the body, in
this order: muscle, liver, fat cells.  If you have abdominal weight gain,
you have hyperinsulinemia/insulin resistance)

Rob