Macroelements are a lot like hunger, however it is divided into three groups, carbs, fats, and protein. Fats and protein decrease at roughly the same speed, however. They decrease the slowest, roughly 100 minutes until you are out. Carbs decrease faster, roughly 75 minutes until you are out.
Meter rate of decay, effects at low levels, effects on health are unknown at this time.
The list of effects is here