Why sugar and starch are to avoided as much as possible.

"Dietary fat in the presence of carbohydrates (sugar and starch) behaves very differently than dietary fat in the absence of carbohydrates. The dietary fat in the presence of sugar and starch is far more likely to be stored as excess and also to become damaged through peroxidation, as the body looks to preferentially burning off the sugar to get the excesses out of the bloodstream quickly and as... sugar combines with the fat to damage it and make its presence more problematic than it otherwise would be. And as long as insulin is present (in other words, as long as dietary sugar and starch keep coming in) it becomes impossible to burn fat at the same time. Weight gain is the most common consequence, but there is more to this. You can be skinny and athletic and also suffer serious consequences from a dependence on sugar burning." -- Nora Gedgaudas