If a fatty meal has been ingested, the liver and gallbladder need to be alerted about the need for bile. the receptors that are responsible for sensing the fat in the ingested food are refered to as

The answer would be chemoreceptor.
Chemoreceptors are a group of the receptor that could detect a specific chemical substance. The substance varies, it could be oxygen, carbon dioxide, sugar, amino acid or lipids. The chemoreceptor that detects fatty meal should detect the lipids in the stomach. 

Atp is is our little "pocket" of energy. of course, if you have too little, then it means you have too little energy, and you'll pass out. the way to not have enough, is to have no energy sources (glucose, fats, proteins). you can't have too many atp molecules. cycles like the krebs cycle produce it, but if you have too much of any substrate (or too little for that matter), the cycle stops and atp is no longer made (it stops until substrate levels are such that the process can go on). in any case, this is unlikely since atp is constantly hydrolyzed and remade, even while you're asleep. you won't have too much. if you have zero, you are dead or dying.