Is there a way to change the kind of body that npcs spawn with?
In game? Anyone you've exchange contacts with you can edit any way you want from the contact menu.
For all randomly generated characters in game? In the "esc" menu there's an entry called "NPC distribution & Beauty Standards". Next to the names for most of the presets the game uses there's a checkbox and if you check it the game won't use that preset when randomly generating a new NPC. There's presets for various body types and things. So, for example, check one of the fat bodies and you'll never see someone generated with that fat body in your game. You can also change the degree to which a preset is considered "attractive" and that combined with the "average attractiveness" setting can make certain presets more likely to be used than others.
When writing scenes?
generatePerson(preset1, preset2, ..., presetN)
Generate a new actor. If nothing inside the bracket: completely random actor. Or you can specify the presets to blend into this new actor.
Presets are just the ".lpcharacter" files created when you save something in the character creator. Save a character called "doctor.lpcharacter" and then call the function "generatePerson(doctor)" and the charcter the game generates will be exactly the same as the one created and saved including the stats if you chose to set those up and save them too.