[everdev]

I'm not sure potatoes are the problem.

The problem is carbs give you short term energy. It's great and healthy if you're doing manual labor, playing sports, lifting weights, etc. or otherwise burning that caloric intake.

If you're watching TV and eating carbs your energy boost is wasted and can get stored as fat.

And sugar as far as far as I'm aware is never healthy but can have less of a health impact in very small doses.