Lack of sleep has what effects on matabolism?

Probably slow it. Lack of sleep does no good to any part of your body. Though different people respond differently to different stresses, after a prolonged lack of slewed your metabolism would probably slow down, though nothing is known for certain.

Related Questions

Can lack of sleep slow down one's metabolism?

Sort of. Sleep deprivation messes up several hormone systems which can affect metabolism is various ways. It can make you crave certain foods (usually heavy carbs which pack on the pounds) so this can also play a role. Read more...