Fat is the most efficient molecule for long-term energy storage, even compared to carbohydrates, because
a. with their numerous hydrogen atoms.
b. fats provide an abundant source of high-energy electrons fats can directly enter the electron transport chain, the phase of respiration that produces the most atp compared to carbohydrates.
c. fat produces fewer toxic by-products when it is metabolized when compacted.
d. fat occupies less volume than an equivalent amount of carbohydrate p.

d.

Explanation:

Your body uses two types of molecules for storing energy, the carbohydrates are the main type and its used for short term storage, and for immediate use by the body. And the lipids or fats, are used for long term storage in the body, because they can store more energy in the same volume than a carbohydrate.

"1. it should be, it has been for about 20 years, and it's really not much different in the end than breeding animals to have particular traits. there are always concerns about genetically engineered animals/plants affecting the environment in unexpected negative ways, but i can't think of an example where the fears didn't turn out to be baseless.  

first, as you point out, it would be a great advance in pharmacology, to be able to tailor drugs and their doses to me. the pros involve better medical treatment. the cons involve privacy issues like insurance companies denying coverage to people with genetic risk factors. looking at dna markers wouldn't affect the frequency of genetic diseases, but it would allow detection of them earlier. and ok, actually i suppose that if people used this information to avoid having children with genetic diseases, some might decrease in frequency."