Being Young!? This one's quite a surprise, but a 2010 study found that women between the ages of 27 and 45 had more sexual fantasies as well as sex, than the ones between 18-26. Go figure...
Propecia. A 2011 study has found hat this hair-growh drug causes erectile disfunction and low sex drive in men.
Undereating. Calorie restrictions are obviously going to make people tired and probably grumpy, which don't bode well for sexy time.
Overeating. Saturated fats are especially dangerous to our sex drives, because they clog arteries, restricting blood flow to sexual organs.
Depression. This is obvious. Loosing interest in everything including sex are the known symptoms of this disorder.
Antidepressants. Some studies have found a link between lowered sex drive and some antidepressant drugs.
Sleep Deprivation. It's proven that getting less than 5 hours of sleep, drastically lowers men's testosterone levels, therefore decreasing sexual desire. It's fair to assume that tired, sleep deprived women won't have sex on their minds either.
Birth Control Pills. A study conducted in 2010 on over 1000 women has indicated that those who took birth control pills had decreased sex drive.