The average American consumes about 150# of sugar per year (I've seen estimates ranging from 135 to 185). Hunger is a God-given desire. God built hunger into our bodies so we would eat the food we need to get the nutrition we need to be active and healthy.
Say we need about 2100 calories a day. In the Garden of Eden we could wander around and our hunger would lead us to eat about 2100 calories of the goodies there (carefully avoiding the apples or whatever that forbidden fruit really was) and in so doing we would get all of our nutritional needs met: fat, protein, vitamins, fiber, minerals, etc.
Now say that each day we eat 1400 calories of that good nutritional food and 700 calories of sugar. What's the problem? Obviously we are only getting about 2/3 of our actual nutritional needs met now.
If we consume 700 calories of sugar a day we either need to eat 2100 calories of real food (for our nutritional needs) and the additional 700 calories of sugar will make us gain one pound every five days or, if we limit ourselves to 2100 calories total we rob our bodies of much of the nutrition they need to function at their ideal capacities.
And yes, 150# of sugar works out to approximately 700 calories a day.
My problem is I'm training hard this month, which means I need an extra 1000 calories a day, and I can't figure out how to do that without eating a lot of sugar and fat (I'm not feeling much sympathy here!). Well, I know how to do it in theory, but I get tired of fruit and whole grains after awhile.
In fact, if there were any donuts in the house right now...