[cco]

This always surprises me as cutting out refined and/or unrefined carbohydrates has no effect on my weight.

The only thing that moves my weight down is reducing calories or increasing activity while maintaining the same caloric intake. I suppose it's entirely possible these people are doing the former and just don't know it.

[GordonS]

I think that quite often reducing refined carb intake is quite likely to result in a reduction in calorie intake - when our blood sugar rises and then falls, it triggers feelings of hunger, making snacking more likely. With unrefined carbs, the GI is typically much less, resulting in a slower rise of blood sugar to a lesser peak.