She said nutrition dense, that doesn't mean fiber necessarily....it could be micro nutrients or protein. Maybe you should learn to read before you reply.
Also, fiber (both soluble and insoluble) still contributes to calories and sometimes can block the absorption of micro nutrients.
She was talking about "Nutrient Rich" diets, which are naturally high in dietary fiber. The reason they are low calorie and still nutrient rich is because they are rich in nutrients like vitamins and fiber instead of things like trans-fat and high glycemic index carbs. This ends up turning any other nutrients you eat into a longer lasting form of energy by slowing down the absorption. Instead of eating something that is digested quickly then takes forever to move out of your bowels, you end up with a steady, constantly moving digestive system that is never getting clogged or damaged. This also gives you a steady uptake of nutrients throughout the day so you don't get worn out as quickly.
When your digestive system is healthy, you naturally absorb more nutrients, you keep your digestive system clean, and you don't get constipated all the time.
And the reason I called you a smartass is because of how rude your post was, and the post before that was laughing at someone without even giving an explanation. When you go around trying to make fun of people instead of trying to add to the discussion it shows something about your motives and maturity level. And who would want to take diet advice from somebody whos diet obviously isn't helping their mood?