Orexin is needed to produce brown fat which burns fat.so people with narcolepsy have orexin deficiency , so can people with narcolepsy still burn fat?

Yes: Great question! yes, people w/narcolepsy can still burn fat. It's just that it's more difficult to get physically active when one can't get a good night's rest.

Yes they can: Recent literature does suggest a link between obesity and narcolepsy via the orexin pathway. And yes, models have shown orexin acts on brown fat. But lipid metabolism is complex and there are other pathways to catabolize the lipids. So, narcoleptics can "burn fat" but probably not as efficiently. Hope that answers your question!