Hi,

I don't understand how long carbohydrates last in the liver to be used up by the body. I know that the cells will take as much energy as they need when you have consumed carbohydrates, but let's say there are suger left over in the liver which will be stored as fat, HOW LONG WILL THE SUGAR STAY IN THE LIVER BEFORE IT'S STORED AS FAT? Maybe after a while you'r cells need more energy, but the sugars has already been stored as fat?

Liver can store both triacylglycerols and glycogen for energy.  Glycogen is a polymer of glucose.

CMIIW 

Sugar was converted in to fats when glycogen (glucose reserve, kept as its polymer form) fulfilled because glycogen storage has a limit, and the capacity of glycogen storage was differ one people to another. One factor is muscle mass, because glycogen is stored in the liver cells but also in the muscle cells. So, people with bulk muscle can keep more glycogen. 

When glycogen storage fulfilled, the excess sugar will converted to be body fat (Excess sugar cannot be excreted via urine and feces (except in diabetes condition due very high blood glucose level), but is reabsorbed and stored as valuable energy source reserve). But it is different between glycogen and fat storage, fat storage is almost unlimited so it can cause obesity.