Carbs to sugars which triggers the pancreas to produce insulin. Too much and this triggers the liver into producing triglycerides which turn into fat cells. Am I correct? Or something along those lines, heh.
Excess in energy
can be stored as fat. But what is too much?
The liver glycogen levels would have to be filled first, then the muscle glycogen levels. Even the blood stream requires small amounts of glycogen as well as other organs. If any glucose exists after your two major storage tanks are filled up, chances are you store the excess energy in fat cells.
If I ate too much protein, I can get fat. If I ate too much carbohydrates I can get fat. If I ate too much fat, I can get fat. If I eat too much of anything, I can get fat. What does it boil down to? Calories.
There are cultures that practice high carb diets, high fat diets and high protein diets, yet they still stay lean. There are associated health risks with each of these cultures. No matter what, there isn't a perfect diet. A well balanced diet is what I aim for and I wouldn't go to any extremes as to cutting out any of the major macro-nutrients.
If I kept my diet as is, and cut out any particular macro-nutrient group, I would be in a huge caloric deficit which would force me to lose weight. But there are always trade offs when you cut out/add fat, carbohydrates, and protein.
There will always be studies that say, you'll have "x associated risks" in either a high fat, high carb or high protein diet. Usually a vast number of these studies will become outdated, disproved, contradicting or irrelevant.