Three Questions about Sexual Desire I am wondering a few questions in regard to sexual desire and Buddhism.


Is fantasizing a form of craving and thus worse than sexual activity without it? What are the mental processes involved?
How much does a single orgasm, for example, affect the spiritual path? Basically what is the magnitude of the effect?
Is it possible that some individuals cannot eradicate lust and should merely diminish it?
Is fantasizing a form of craving and thus worse than sexual activity
  without it? What are the mental processes involved?


Fantasising creates further sexual energy that adds to the momentum of the whole process. Mental visualisations and thus sensory pleasure being the 'wanting' component.


  How much does a single orgasm, for example, affect the spiritual path?
  Basically what is the magnitude of the effect?


An orgasm doesn't effect the path in the slightest. How you have come to achieve the orgasm does. This can be a bit of a grey area for some. Sexual encounters are still possible for a practicing Buddhist but sometimes it's helpful to refrain from sex for a time in order to learn about how your physiology is guided towards the wanting of sex.


  Is it possible that some individuals cannot eradicate lust and should
  merely diminish it?


If you practice ardently, diminishment will be the first occurrence. It's not helpful to want to eradicate a natural biological process. It will create frustration (dukkha) but it may be a great learning curve if you're well versed in the arisings of your own suffering. Essentially, just work towards learning how it shows itself in your body and actions.